Watch the Level 1: Beginner Classical online guitar lesson by Andrew Leonard from Take 5: Beginner Classical
The main focus in learning to play "Greensleeves" is the melody. The arrangement I made uses a very minimal amount of bass and accompaniment notes, so the melody can be easily heard and played. This will also allow you to experiment with dynamics and apply some of the different "classical guitar style" suggestions made in the breakdown. Be sure to stick around for the great performance opportunity suggested at the very end of the breakdown!
Also, keep in mind you are playing a sorrowful song. I always spend practice time playing the melody alone, for each piece I am playing. I do this to make sure I always keep the mood of the piece in mind, make sure I'm playing expressively and using dynamics. I'm always asking myself, "am I using a crescendo (getting louder) or a decrescendo (getting quieter)?" By experimenting with different dynamic ideas, I gain a better insight into the music I'm playing.
Remember, you can consult the lessons materials for tab and standard notation that includes right and left Hand fingerings. Every note has been labeled for both hands. Again, classical guitar notation for the right hand is P, I, M and A and the left hand is 1, 2, 3 and 4.