If you are using the Call REST action, then in the Response tab there is an option to Commit the response. This will store the response in the Mendix database.

https://docs.mendix.com/refguide/call-rest-action/#response

If you want more flexibility you can manipulate the List in the calling Microflow before committing the data using a Commit action or a Change action with commit selected.

https://docs.mendix.com/refguide/committing-objects/
https://docs.mendix.com/refguide/change-object/

Hope this helps.

In your Rest Call action, you can configure to apply an Import Mapping. There, you can also choose the commit behavior of the mapping: you can choose to either commit, commit without events, or not commit imported objects.

If you want to commit only specific parts of the result (or just have a bit more flexibility), you can also not commit and store the result in a variable (which likely has a root with the list associated with it). Then, you can retrieve the list of objects attached to the Root (with a normal retrieve action) and commit that. 

Some more information can be found here:

• https://docs.mendix.com/refguide/import-mappings
• https://docs.mendix.com/howto/integration/consume-a-rest-service/
• https://docs.mendix.com/refguide/call-rest-action