There aren't any instructions for this on the mojoPortal site.
A brief overview of what needs to happen is:
Create new website on new IIS server.
If you are using Host Headers (Bindings in IIS 7+) on the new server, set the website to use the correct domain(s).
Zip contents of current mojoPortal website on current IIS server.
Extract contents of zip to the new website on the new IIS server.
Set read/write permissions on \app_data and \data directories of new website on new IIS server.
If your database server and webserver were the same machine but are now different machines, adjust the database connection string in the user.config appropriately.
Change your DNS to point to the new IIS server.
Moving mojoPortal to another server is just like moving any other web application. You need to verify the new server meets all requirements of the application and that it has access to the database server.