This article assumes you have already got the source code for mojoPortal from the source code repository.
You must have Visual Studio 2017.
Setup your database, either MS SQL, MySQL, or PostgreSQL. If you want to use SQLite, you don't need to setup the database, it will be configured for you when you run mojoPortal the first time.
Open the mojoportal.sln file in Visual Studio.
Choose the build configuration corresponding to the database system you want to use and then rebuild the solution.
Rename the user.config.sample file found in the root of the mojoPortal.Web Project to user.config.
Edit the database connection string in the user.config file. Note there are connection string settings for all supported databases, make sure you edit the one for the db you are using. The settings in the user.config will override the settings in the web.config. This is especially handy for working from the repository because you can get updated web.config settings without any conflicts. Be aware that changes to user.config are not detected right away like changes to web.config so sometimes in order to make changes in user.config take effect, you have to type a space into web.config to change it in order for the updated user.config to be picked up.
As long as your db is setup correctly and your connection string is correct you should be ready to go. If you got everything right you should now be able to click the Play button or choose "Start Debugging" from the Debug menu. This will compile the solution and open the site in the browser. The very first time you run it, it will throw some exceptions because there is no content yet in the db and the upgrade scripts have not yet been run. Just keep clicking the Play button (or F5) to continue execution, it will handle the exception and check if it needs to run upgrade scripts. It will run these scripts automatically as long as you don't stop execution.
Debugging With "Other" Web Servers
If you need to debug using a web server other than the one built-in with Visual Studio, follow this documentation from Microsoft.
There are some video tutorials here that may also help: http://www.mojoportal.com/developertrainingvideos.aspx
Visual Studio Performance
People often ask about how to make things go faster in Visual Studio, the mojoPortal solution is very large and it can be very time consuming to rebuild all of the projects especially if your development machine is not very powerful. Visual Studio is a resource hog and really requires a pretty powerful machine, when you factor in that developer time is very valuable it makes a lot of sense to get the most powerful machine you can afford to make best use of your developer(s) time. But in the final analysis you must work as well as you can with the machine you have, so this article will suggest some ways of working in Visual Studio more efficiently.
Use The Debugger Only When You Need It
Often I see developers running their web projects in the debugger for no reason at all and this is the slowest way to work. The debugger is a tool for stepping through the source code at runtime to find out what is happening vs what you expect to be happening. If something isn't working right you should set break points in your code and then step through it with the debugger to learn what is happening. But this is not how you should work normally, only when you need to actually step through the code. Once you have built the entire solution at least once, then to run the project all you need to do is right click the Default.aspx page in the root of the mojoPortal.Web project and choose "View in Browser". This will launch the site in the Web server but without running the debugger and it will be much faster than running in the debugger.
Only Build What You Need To Build
Assuming you are working on custom features that are in your own projects, when you make a change you do need to build your project(s) again both to compile your changes and to run the post build event which copies your modified files up to the mojoPortal.Web project. But you don't need to rebuild the entire solution. You should not be modifying the mojoPortal code, all your work should be in your own projects so it should rarely be needed to rebuild the other projects after they have been compiled/built at least once. And as mentioned above you don't need to run the debugger unless you have a need to step through the code, so your workflow should generally be to build your project since it has changes then just refresh the page in the browser, no need to launch the debugger.
There is an optimization you can make on the <compilation section in Web.config to speed things up as discussed in this blog post by David Ebbo, you can add the attribute optimizeCompilations="true". We have this information in comments in the mojoPortal Web.config file. I find it works well in general but occasionally I have encountered unexpected behaviors with this enabled so we don't have it enabled by default. But you can try it and it should help, if you encounter any problems try removing it and then put it back after the problem is resolved.