By default, Luminate will automatically add all constituents to an opt-in group, if the box is selected at the time of creation.
If you notice that the group is not populating, your local settings may be preventing the task from running. Here is how you can run and activate the task manually:
  1. Select Data Management > Tasks
  2. Search for the task associated with the interest group (usually has the same name as the interest)
  3. To run the task immediately, click Run. If you do not want to run the task immediately, skip to Step 4
  4. To have the task run on its recurring schedule, click Activate
  5. Once the task runs, the associated interest group will reflect new members 
Please note that once the task runs, you may need to manually refresh the group information summary to see the updated group member statistics.