Watch the I vi ii V Etude Level 1 online guitar lesson by Vicki Genfan from Open Tuning Handbook: Rhythm
Practice the strumming pattern first and make sure you have that down. Let the strings ring out at the end of each measure. Try the fingerings I've used, but feel free to switch fingerings if you feel more comfortable. Just remember – the least amount of movement between chords, the better. Use your thumb muting skills to mute the 6th string on the vi and V chords.