It’s picked with your fingers and you’ll want to let it ring throughout the riff. It can be performed on either acoustic or electric.
Here it is looped at normal speed (90 bpm):
Now, let’s break it down into 2 parts. The 1st part will consist of
the 1st 2 measures. Use your thumb to pick the notes on the G string,
your 1st finger for notes on the B string, and your 2nd finger for notes
on the high E string.
Here is the 1st part looped at a slower tempo for you to isolate and practice:
The last 2 measures of the riff is the hardest to play. The suggested fingerings are shown below the tab staff below. The fingerpicking is a little different here. Use your thumb for notes on the D string, your 1st finger for notes on the G string, your 2nd finger for notes on the B string, and your 3rd finger for notes on the high E string:
Here are the above 2 measures looped at a slower tempo: