Server groups enable you to organize sets of panel modules together, and tie that group to a product or products. For example, if you want to sell Plesk hosting, and you have five Plesk servers, you would create a single server group and add all five panel modules to that single server group. Then, while setting up your products, you have to option to tie each product with a server group - for your Plesk hosting products you would choose the Plesk server group.
You can reach the server group page by clicking System -> Server Settings -> Server Groups. Each server group can have only one type of control panel. This includes differences between Plesk for Linux and Plesk for Windows, for example. These are different panels, working with different kinds of servers, so they must be in different server groups.
By default, your system comes with a server group already created. If you only need one server group, you can simple configure the default group. If you need additional server groups, you can add them by clicking Add Server Group in the upper right hand corner of the server groups page. On the second page, enter the name you would like to use for the server group. This is not something your clients will see, so it can be whatever is meaningful to you. Then choose the fill type you would like:
Please note that fill type rules only apply if you have more than one panel module configured in the server group. Otherwise, ModernBill will just add all new accounts to the one panel module.
Once you've created a server group, you should be taken back to the main server groups page. From here, you should see your new server group, with the words Add a Panel and a drop down menu visible next to it. Choose the panel type you would like to add, and click add. Information on setting up the various server modules can be found on the server modules page.