The vast majority of .22 silencers are just direct-thread, so just screw it on. It's up to you if you want to unscrew the flash hider every time, but I'd just use a thread protector if I were you. But most people who have .22 silencers rarely shoot without them; I doubt you'll shoot your rifle unsuppressed very often.
But make sure you get a thread spacer before you thread on your silencers and shoot them. AR-style .22s usually have longer AR-style threads and most .22 cans won't butt up against the shoulder, which can cause baffle strikes because the silencer isn't properly aligned. And some silencers might butt up properly against the shoulder, but the muzzle will be too close to the first baffle, which can be an issue with asymmetric baffles. For example, the Spectre II will still shoulder properly on an AR-style .22, but the bullet exits the muzzle so close to the first baffle that the bullet becomes unstabilized and can keyhole. The one time I saw this happen, the shooter was very lucky he didn't get baffle strikes.
Gemtech makes cheap 1/2x28 spacers; make sure you get one before you shoot your AR-style .22 with a silencer, otherwise you could get baffle strikes and destroy your new cans.
