the handle has a set screw more likely allen type. remove that first. Then the sleeve can pull off. put if you want the whole valve, gotta go behind it. Or are you just talking cartridge?
I can't unscrew it using the Allen wrench. It might be corroded. I tried to put WD40 but it's still not coming out. Which way should I turn the Allen wrench? Clockwise or anti clockwise?