You can check guests in directly from your computer, however we advise you to use the iOS Check In App as it is much more robust and suited for the task. Checking in via a computer requires an active internet connection, while checking in from the app does not. Additionally, scanning tickets is only possible via the app.
From the list of tickets, click the Check In button.
Once checked in, the green button will change to a yellow "Check Out" button so you can undo the check in.