Installing a new lift

Turn chair on its side. You may need someone else to help by steadying the stool while hammering.
Using a soft blow mallet (preferred) or hammer, strike on the edge of the chrome lift that is extended through the bottom of the base. It may take a couple of sharp blows, so don’t be afraid to hit hard.
Once base is off, strike seat bracket around the place where the lift is connected, (a soft blow hammer is preferable; otherwise, use the regular hammer), pulling on the lift as you strike. It is helpful to have another person pulling.
Put new lift into hole of base, place seat on top of lift, and sit on chair to secure.