Use your yard stick or meter stick to determine the height of the space between your ceiling and floor to ensure an 8-foot adjustable steel post is exactly what you need before purchasing it. You can find it in a hardware or home appliance store.
Cut out and place a block of lumber on the spot where you want your steel column to go. Put your steel column on top of the wood block and turn your adjustable top so it moves upward.
Raise the ceiling above you by turning clockwise the lever that joins with the steel column. You should never raise the ceiling greater than a 1/4 inch per day. You might even need to build an additional temporary beam to disseminate the force of multiple jacks across the stretch of several floor joists. A 4-by-4 or a 6-by-6 will make an adequate makeshift beam, or you can nail together multiple 2-by-6s to create the same effect. Your floor joists may be sagging due to poor design or simply being old and worn. If this is the case, place multiple steel posts beneath an 8-foot makeshift beam that spreads across seven floor joists 16 feet apart from each other on center. To do this you probably need three columns equally distanced beneath the beam. Raise each slowly by going a 1/4-inch at a time until you've reached the lift you desire.