Can't get the click and back off of my walkie talkies to change

The batteries. I DID put the batteries in in the first place, but have lost the instructions and can't get the backs off. It is a Midland X-TRA TALK. model xt18

Sorry, but Midland has apparently disowned that model, and I can't locate any info on it. If the case is similar to my Midlands though, there's a clip, about 3/4 inch wide, at the bottom of the rear of the radios (below the belt clip - if installed). Place a finger, coin, or screwdriver (gently) into the indent at the top of the clip and pull downward. It should swing down to let you remove the battery cover.

I had problems removing mine also. 1st remove the clip. With the back of the radio facing you push down firmly with your thumb and slide it off. At 1st I didn't think mine removed but after some extra force I was able.