There are multiple ways to bulk-add supporters to a group. The best path forward depends on your particular scenario.
Scenario #1 (You have a list of the supporters.)
If you have a list of email addresses (or, less likely, supporter keys) for the supporters that you're wanting bulk-added to the group, then our recommendation would be to use the 'Supporter > Import Supporters' tool for adding them:
If the supporters already exist in Salsa, then, using the import process, you'll really only need a single-column import file to identify them (usually just a list of email addresses). In the 2nd step of the import process, just be sure to Field Match the appropriate field (again, usually Email) and choose the group that you'd like to place them into.
Scenario #2 (You have conditions for finding the supporters.)
If the supporters already exist in your Salsa list AND you have some conditions for how to locate them, then our recommendation is to use the (Supporter > Query/Export) tool to bulk-add the supporters to a group:
In the first step of the process, you'll need to design a Query which will return the supporters. Here are the terms available:
After you run your query, you can add them to the Group of your choosing, in the 2nd step (the 'Take Action' step).