A building can only helped once at a time. You need to either collect from it or store and place it to allow others to allow the next person to help it. Helped buildings give a bonus of 1 extra xp and 20% extra income. Of the four building types all but crafting ones can be helped.
Oh, yeah...about getting your game to level-up, right? You're welcome! So happy it helped!
Am I the only one with a purple cow problem:-/...?