Are you referring to the outer staging cylinders?

If so, you remove whatever retains the top of the rod in the mast. This can be a bolt or a snap ring. You then lower the forks completely to ensure there is no hydraulic pressure left in the cylinders. Raise the mast with straps and another forklift or an overhead crane. The outer cylinders should stay lowered. You then remove any cylinder restraints and the lower hydraulic hoses to the cylinders. Depending on mast design, you can either remove the cylinders out the top or angle them and slide them out the bottom. Be careful.