Here’s what both the guitar and bass sound like together:
This riff is in drop D tuning. In drop D tuning the low E string is tuned down one whole step to D.
For this riff you’ll need to use a slide. Place the slide on your 4th finger. Much of the riff is played without the slide. The slide is used to play the notes on the 6th fret in the 3rd measure and for the entire last two measures of the riff.