For the purpose of arranging, all melody notes are written with the stems pointing upwards. This is done to visually distinguish the melody from the accompaniment, which has the stems pointing downwards.
The key of A minor has been selected for two reasons:
When you are doing your own arrangements make sure that the melody is in an easy key (e.g., C, G, Am, Em) and that most of the notes can be played on the first three strings.