Let’s begin by learning the First Finger Pattern, which is a pattern of:

1st to 2nd finger: whole step
2nd to 3rd finger: half step
3rd to 4th finger: whole step

The steps between 1st and 2nd, 3rd and 4th fingers are called a tone.
The ‘close’ or ‘half’ steps between the 2nd and 3rd finger are called a semitone.

Try the pattern of notes on your right arm. (Bring your right arm up to your body so that you can see while placing your fingers)