Universal toilet seat, this kind of toilet seat is the easiest to replace.
Just wipe the toilet gasket clean and stick the adhesive toilet seat along the gasket.
For zipper toilet seats, wipe the toilet seat clean, cover the clean seat from the inside, and pull the zipper.
To replace the hook-and-loop toilet seat, wipe the toilet gasket clean, place the hook-and-loop toilet seat on the spacer, and finally stick each pair of hooks together.