Wonderlin, you just do P1 until the cravings go away. However, if you can't tell that the cravings are bad or are not sure how long it takes, I'd do it for 5 days. Most people are able to detox from sugar in 3-5 days. Definitely don't do it for more than a week.
I just jump back into P2 afterwards. If you already know your "combo" (the Phase 2 combination of foods that works for you), then you can just go back to that. If you're still figuring it out, then you can go back to the last step you were on (for instance, you'd figured out that you could have 1 fruit and 1 starch a day and were trying 2 starches to see if it worked).
Hope that helps!