How do you remove slave cylinder hose for an 89 ford f150

First thing I would do is obtain a replacement and match it to the one that is currently on the truck.
One end or the other will likely have a hose thread into it and the other may or may not have a "banjo" bolt that bolts through it with sealing washers. Save those washers if the replacement doesn't have new ones.

After replacing the hose, let it gravity bleed. That usually takes care of any trapped air. Test it for proper operation before driving the vehicle.