If there is a reservoir ( and it has a breather cap) and it's a piston cylinder then any air in it will work itself out after a few cycles. A lot of the underbody hoists had a little air bleeder screw in the top where you fill them. If it does not don't worry about it but if no reservoir then just fill to near full and run it up and down a few times. you can use a pipe plug and drill an 1/8" hole in it and put small cotter key in it to keep dirt out but it will allow for expansion of the oil.
