You need to use inverse kinematics. Right-click on the .skel (the round bulb/globe around the hip) and select Inverse Kinematics. Select the "Move" function under the "Modify" tab. Grab a bone, move it. If the mesh moves, great. IF not, check that it's weighted. If it's already bound to the skeleton (sometimes it happens automatically, think it has to do with the skeleton being similar across some models) you'll see a "null" warning above the "binded to mesh" message. BE SURE TO RESET TRANSFORMATION after moving skeleton bones.
Also, for whatever reason, some weights do not copy correctly. I've seen this a lot with the uppr. Need to select the actual bone (use the hierarchy tree) and right-click, then "set as current bone". Make SURE weighting paint is visible in the 3D viewer. If you select an arm bone, ,hand, etc., you should see weighting paint. If you select something like SKEL_Spine3 as current bone, the entire upper should be showing paint. Sometimes, the paint will not match the bone. In those cases, selecting SKEL_Spine3 will show nothing, but SKEL_Spine2 will show something like uppr or arm paint, etc.. That's NOT correct. When using Inverse Kinematics with it like that, moving an arm will cause the entire mesh to move and immediately distort. In those cases, reset transformation and try a different ped to COPY weights from.
Also, Oleg is pretty good about responding in his GTA V forum under the zmodeler 3 section, so any super-tough questions, can always ask there.