I am trying to learn to finger 'March in f' by Daniel Turk, but it's driving me nuts how to do it.
It's in 'Essential piano repertoire', selected and edited by Keith Snell (preparatory level, page 7). Any tips would be helpful and nice.
The little numbers above the notes are meant to indicate which finger to use to play each note. For example, in the image in your question, there is a 3 above the first note, and then hand-written there are the numbers 4, 3, 2, 1 above the notes of the descending part at the end of the first measure.
The fingers of both your right and left hands have the following numbers:
So that means for the right hand part in the picture, you play the first two notes with your middle finger, then use your ring finger to play the third note, middle for the fourth note, index finger for the fifth note, and thumb for the sixth note (the last note of the measure).
Notice that you don't have to move your hand at all to play the notes with the fingers as written. Usually finger numbers are chosen and written in to allow for the minimum of hand movement, especially for beginner pieces like this one.