Lavender’s Blue is a simple tune in the right hand only that uses the first six notes of the scale of C Major. For the lowest five notes C D E F and G use all the fingers or your right hand - one for each note. (With your thumb on C and your little finger on G). Then for A just stretch your little finger to reach that note.

Hint: To help find the notes ensure Show Note Names are turned on from Setup Preferences menu.