From where do I access Entrance 12 Main Stand?

Trying out the Main Stand Upper for the first time on Saturday on the side nearest the Gil Merrick, but I can't make out from any of the stadium plans where the hell entrance 12 is because of how poor all the maps are. Do I access it from St Andrews Street where the Gil Merrick entrances are, or is it around the other side on Garrison Lane just round the corner from the Tilton Entrances? Would appreciate if anyone could mark it on a map for me