A Process Group is a grouping of Processes. 

For example you may decide to have a Process Group called Assembly. And you may have a various Processes in that Process Group, e.g. Preassemble, Assemble, Install, etc.

 To set up a new Process Group, from the main menu go to Set Up > Process Groups.

       

To add a Process to a Process Group, from the main menu go to Set Up > Process.  Next to the Process you wish to edit, click Edit.

       

Change the Process Group Name to the one you require.