Spritekit nodes have position and anchorPoint CGPoint properties. I found the behaviour of these two properties confusing at first. Especially when adding multiple levels of children using SKNode’s addChild method. So here is a “cheat sheet” if you like, a visual helper that explains how it all works. If you’re as confused as I was then studying these examples should help.
http://www.garethelms.org/2014/06/help-with-spritekit-position-and-anchorpoint/