In lesson 12 you learnt the key signature of F major, which consists of a Bb symbol written after the clef. Pieces which contain mostly notes from the F major scale are in the key of F major. Here is a piece which you have already learnt in C major, this time transposed to F major. As you learn more keys, it is important to transpose all your melodies to every key. Professional trumpet and cornet players are often required to transpose music on the spot, so the more familiar you are with transposition, the easier this will be when you are asked to do it.
Don't forget to practice your arpeggios in each new key too. Here is an exercise to help you become familiar with the F major arpeggio.
As mentioned earlier, the more familiar you are with the notes of a major scale played in any order, and the arpeggios based on the scale, the easier you will find it to play melodes in that key. Here are some examples using arpeggios derived from all the degrees of the F major scale.