Take the pot and crush it really thoroughly. It's tough to roll with any big (or even small) chunks. Once you have a decent amount, take two Zigzags, lick one and stick the other to it, making sort of a wide paper. Grab the pot and put it on the paper. Roll it vaguely like one would do while rolling cigarettes. Once you have it looking like a cigarette, roll one end really tight. Grab some heavy paper, like the jacket off of the Zigzags, tear a piece off, and roll it to approximately the diameter of the joint. Stick it down into the open side of the joint, compacting the pot a bit (not too much). You'll hold the joint from this end. Once it's as good as it's going to get, lick the open end's paper and adhere it to the heavy paper cylinder. Light the rolled-up end (not the heavy paper, but the rolled-up Zigzag end), let the excess paper burn off. You know what comes next.

Warning: This is extremeley difficult, especially when you've had a few. Get someone to show you, or, better, get someone to do it for you :)