We'll keep trying some other simple tunes. Try the one below, remember just get to the point to where the notes are ringing clear and you are changing fingers smoothly first, then worry about it sounding like 'Yankee Doodle'...

Your fingers will ache and hurt for a few weeks. Specifically the tips of them, until you get some callouses. You can keep your fingers stretched and limber by 'walking' up and down the strings. For example, start with the low E string(thickest), and fret with first finger on the first fret. Now play that note and then fret on the same string on the second fret with the second finger...once all four fingers have fretted move on to the the next string...you are 'walking' the strings!

These simple finger exercises will help get your fingers into playing shape and help them 'learn' where and how to fret the strings.