When custom modules are created an enabled in the account, they will be listed in all users' main dashboard assignment status chart. If they are assigned as a project or stage assignee of a record in that module, they will see the assignments in this chart.
Clicking on the bar in the chart will drill down the data table to start the assignments. Clicking on the Key ID of the item will open it.
The record will open with the details listed at the top and then the open stage that the user needs to complete.
Once the stage is filled in, the user will need to send the stage off for approval and transition the record to the next stage.