I'm confused, are ya playing a really old version of turok? the current editor version is 1.05, perhaps you should get an updated version.
Yes for GOG you need to play the editor.exe
To playtest your map, go into your root folder, open config.cfg, find seta developer "0" and change the 0 to 1, open your custom map in the editor and press the little play button on the top toolbar.
It should bring you to your map immediately as long as you set a player spawn point on sectors, but if it only brings you to the main menu, open console with the tilde key and type "map <path to map>.
There is no undo option, so save constantly and make a backup.