Watch the Week 3: Metronome on 2 & 4 - Part 1 online guitar lesson by Roberto Dalla Vecchia from Flat Out Flatpicking
This video is about playing guitar with the metronome on the 2nd and 4th beat: it changes the pulse of the music. Lots of fiddle tunes have this type of pulse.
Try to play a simple back up pattern to it, for example: bass strum, bass strum. It's not easy, so take your time and be patient. Get familiar with it, then try to play the backup for "Blackberry Blossom". Don't forget to use the TAB included with this lesson.