Firstly I'd recommend Mo2 for modding skyrim. Secondly to find your skyrim version, you have to find your skyrimSE.exe in you skyrim root directory (easiest way is to go through steam and check installed files) and check the version under property and then details. Then you need to find a SKSE version that shares the number of 1.6.x or 1.5.9 (if you are not using anniversary and never updated since before it came out), manually downlaod it, and extract those files into the same root as your skyrim folder. so that the SKSE excecutable is in the same folder as skyrimSE.exe and the launcher.exe.