1) Hover over the "Microsoft Dynamics CRM" tab, and select "Marketing".

2) Hover over the "Marketing" tab in the top ribbon and select "Marketing Lists"

3) Select the marketing list you wish to change and select "Edit".

4) You can now either navigate to "Manage Members" or click the small plus sign in the members column.

Cannot complete, we have no available members to add so I can't confirm the rest of the process.