Try nothing in this editor works
Once you load your map you aren't going to see anything so have fun making an awesome map that is all black. And as far as adding a player start i'd rather shoot myself q3radiant was much better than this one but it had texture problems cause jk textures were to big and it would shrink them down and your map would look like crap. As far as player starts what i did is open a second jk2radiant and copy an existing info_player_start entitie and pasting it in my map. But when i compiled it and threw her in base dir loaded it in Jk2 map was completly black.