NEWBIE ALERT

Hi,
I'm new to this, and really need some help.
So I deleted the top header block, by mistake, and now I can't seem to figure out how to make a new one. When I create a new, it goes under the menu bar (Greek yoghurt), but I obviously want it at the top. I can't seem to find a way to move it either - is it because I'm working from an iPad?
Secondly, even though I, by mistake, deleted the header, guests can still see the image I previously uploaded there, even though the block isn't even there when I log in?? What's going on?

Please help a novice out......