If your table is like ours on 25RB (secured to wall by window & one table leg opposite side) flip leg up towards table, then there should be a lever under the table, make sure it's in the "unlocked" position then just push down on table top. It will not be an easy push if it's anything like ours, but try pushing close to window where "table slide mechanism" is located and give it a "good" push down . Hope this helps.
Nancy + Tony
'11 Dodge Laramie Longhorn CC
'12 Sunset Trail ST25RB
Ours was also stiff at first, so much that I felt like pushing harder would break something. I got underneath and "helped" that plastic slide along a little bit while putting some down pressure on it. That got things going the first time, now it goes up and down easily with the standard push near the window.