A major scale is a group of eight notes that gives the familiar sound do re mi fa so la ti do. By starting on the note F in the low register and playing all the other notes (using Bb instead of B) up to F in the middle register, you can play the F major scale.
Here is a song which will help you become more familiar with the notes of the F major scale. All the notes here are tongued, so play slowly at first and make sure all your notes clear and even.