Ugh, I wrote up an answer but it got lost in the interwebs -.-
Anyway, this issue has bothered me for a very long time and I finally figured it out. It seems opening the GoLauncher menu is no longer a long press but a glide-up gesture. It takes a few times but it finally opens once you do it just right.
Place your thumb just above the docker (if you're using it). Now. quickly and repeatedly slide your thumb up a few inches. The menu will eventually appear. It is quite frustrating but I can get it to appear after a couple tries with this method. You then can see the menu that allows for adding new screens, widgets, etc.
If worse comes to worse and these directions are unclear, I may have to find a way to record what I'm doing and upload the video to YouTube.
Good luck!