The hex head screw on the side of the dovetail is the set screw for the elevation adjustment screw. You need to loosen that set screw and remove the elevation screw. Then you need to lift the tongue to get to the sight set screw. Be careful because there are two springs under the leaf. You will see the set screw to the side of the hole for the elevation screw. Loosen or take it out and then start "drifting" from the left to the right when looking from the back of the gun. Be advised that Kimber sights are in pretty tight so it might take some force to start it moving. Good Luck!
I think you'll find the adjustable sight is a bit easier to remove than the fixed sights. lictalon is right, you will encounter the plunger spring under the sight. When I took my sight off, it bent over with the sight as I was drifting and I was able to just pull it out without it springing out to that place where you find them with barefeet in the dark.