Learning to read sheet music is easy, but if you don't know the alphabet, you'll get nowhere fast.
Let's talk about the treble staff first -- that's the top staff, has a symbol at the front that looks like an ampersand, or & sign, and is played with the right hand. There are always 4 spaces and 5 lines. The spaces are the notes F A C E, and can be remembered as FACE. The lines are E G B D F, and can be remembered with the mnemonic Every Good Boy Does Fine.
The bass staff is the one on the bottom (both staffs together make the Grand Staff), and is played with the left hand. The symbol at the start of the staff looks like an overgrown comma , . Like the treble staff, it has 4 spaces and 5 lines, but the notes are different: the spaces are A C E G, and can be remembered as All Cows Eat Grass; the lines are G B D F A, and can be remembered as Great Big Dogs Fear Alligators.
All you need now is to know middle C, which is an interstaff note that is always 2 notes below the treble staff and 2 notes above the bass staff; the two staffs can be said to intersect at middle C. It will always have one line through it. It's 2 spaces below F on the treble staff, 2 spaces above A on the bass staff.
The note directly above middle C is D, and immediately below is B.
So, starting with middle C (2 spaces below the bottom line) on the treble staff, you have C D E F G A B C D E F.
Starting with G (the bottom line) on the bass staff, you have G A B C D E F G A B up to middle C.
And now all you have to do is get hold of sheet music and start reading!
Here's a picture of the grand staff with these notes: