Typically you will setup a Check-in in a recurring schedule. If you need to setup a Check-in that you will trigger when you need manually, then you have to pick manual schedule. The setup is similar to creating any recurring Check-in, only in the schedule configuration you pick "manual" instead of "recurring".
Navigate to Troopr home tab where you can see the list of all your Check-ins. Click on "Other actions" ⇒ "Run Now" in your Check-in to start running it immediately.
Answering and reporting behaviour will be similar to any scheduled Check-ins.