To lveldran the key signature tells you what key its in(hence the name) and in this case the their are no sharps and no flats which means it's in C major or a minor. Which to find out if it's major or minor you could look at the end but you would most likely just assume that it's major. And sorry, it's not often that I get to show my knowledge.
It's c d e f g a h c, when you make it flat (the 'b' mark) it becomes c d e f g a b c, and when you put the # on the f line or c line it becomes cis d e fis g a h cis. At least that's how I've been thaught, maybe in America it's different
Just remember....it's very easy. The lines are Every, Good, Boy, Deserves, Fudge. And the spaces are F A C E. There, your part of the our magical super secret, music club! I studied for a long time and I just handed you all my secrets.
That's a way to name those notes, that are also Do La Si Si La Sol Mi
(Please help me spell it)