This short exercise is written in the key of G Major
Notice the key signature at the beginning of the piece.
I have highlighted the F notes, which must now be played as F Sharps.
It is important to take note of the fingering here, as the right hand F sharp note, is played by passing finger 2 over finger 1. This allows the following notes to to be easily played using the correct fingering.
Watch the video carefully, to see how this is done in practice.