As Bednobs' post indicates, Ryanair are no longer operating airport check-in desks. All passengers must check-in online.
If you've got hold baggage you simply take it to a 'bag drop' on your arrival at the airport, and then proceed through security. (Those without hold baggage go directly to security). The only time requirement is that you're expected to be at the departure gate 30 minutes before departure, when the gate (theoretically) closes. In practice the gate won't even have opened at that time. Ryanair flights are scheduled to land only 25 minutes before take off, so the aircraft won't even be at the gate 30 minutes before departure, yet alone boarding! The reality is that the gate will open about 15 to 20 minutes prior to take off, and close a little after 10 minutes before take off. (I've arrived at the gate with 8 minutes to go and had no problem boarding).
If you don't need to use the bag drop you can arrive at the airport just one hour (or even less) before your flight is due to depart. There are sometimes queues for the bag drop desks, so it might be wise to allow a little longer if you've got hold baggage.
Chris