From the Ryanair Website
From 1 Feb all seats on flights will be allocated. Customers’ seat numbers will be displayed on all boarding passes.
Customers may select their preferred seat during (a) initial booking, or (b) Manage Booking or (c) Online Check-In, up to 4 hours before the scheduled flight departure time.
The following seats are available for customer selection:
Premium Seats – Rows 1-5 (rapid exit), Rows 16 & 17 (extra leg room) and Rows 32 & 33 (rapid exit). Available from £/€ 10 (including Priority Boarding)
Regular Seats – Rows 6-15 & 18-31 available from £/€5. These seats can be upgraded to include Priority Boarding for a small supplement of £/€2.
General Allocated Seats – Customers who don’t wish to pay for a Premium or Regular seat can check-in online between 15 days to 4 hours prior to scheduled flight departure and will be assigned a randomly allocated seat at zero cost.
Customers who have already selected Priority Boarding on flights departing from 1 Feb onwards, can now select (free of charge) a Regular Seat (including Priority Boarding) when checking-in online.