There is a bleed nipple on the slave cylinder and you just bleed like normal.
I normally top up master cylinder reservoir to the brim. Connect tube to nipple in a jar with a small amount of brake fluid in it open nipple and let it self drain for a while to help expel air then bleed as normal from then.
Don't let the fluid level drop to low as the clutch cylinder take off is quite high in the reservoir so easy to get air back in if level drops
bleeding the external slaves is simple top up master cylinder leave slave hanging loose carefully pump clutch pedal a few times push cylinder piston back in do this a couple of times then refit never fails.