I don't not if this might help, I'm currently learning android studio, language in use is java. If there is a view on the xml file you just drop the element you wish to place, e.g text, button e.t.c, after which you place your mouse on the borders of the element and move an arrow line toward the edge of the window(phone) for both sides and it will usually be centered. It doesn't have to be the edge it could also be an element.