If you can't find a bleeder screw, you can do this.
You must make certain the hydraulic oil is filled to the correct level before doing this.
Tilt the mast as far back toward the truck as it will go, this is to ensure the carriage and telescoping sections can drop completely to the bottom end of travel when lowering the mast in this operation.
Raise the mast as far as it will go and raise the engine RPM enough to force the hydraulic lift circuit into bypass without killing the engine.
Then lower the mast completely.
Repeat this a few times.
By pressurizing the lift circuit this way (forcing into bypass) some of the air can be encouraged to be entrained into the oil. Lowering the mast quickly and completely after each pressurization helps transport the entrained air back to the tank in the returning oil.
The entrained air will want to come out of the oil pretty fast, so it is important that the mast be lowered completely and quickly each time when you are doing this.
I have used this practice many times on systems that have no bleeds and it has always provided good results.