This tune uses drop D tuning. In the recording, all six strings are tuned down a further full step: C,G,C,F,A,D. So if you want to play along with the original recording, first tune down a full step and then drop you Low E string down another full step. I imagine they use a pretty heavy string gauge because if I did this on my guitar the strings would be bouncing off of the fretboard. In the audio example below I just drop the low E string to D.
Main Riff
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