The "natural" notes don't have accidentals in their name. If you don't know what that means, don't worry. Just follow these instructions:
The "rule" is that the distance between any two notes is 2 frets except between E and F and B and C.
E <--> F is one fret. B <--> C is one fret.
Click on a string on the fingerboard below. The names and locations of the notes on that string light up. Cool! Now play those notes on your guitar and say the name of each note as you play it. Do this going up the string (moving up in pitch) then back down the string (descending pitch) For extra credit, sing the names of the notes (matching the pitch of your voice to the pitch of the note, of course!). Do this everyday until you can do it on every string without refering to this page.