The birth control cycle is good after the first full cycle, after you have had your first period after starting it. This will typically be 4 weeks after starting the first pack.
Birth control pills taken every day generally require two weeks of abstinence, because it takes the pills two weeks to fully affect your reporoductive system.
I am not entirely sure what you mean by safe, but if you mean for you to be protected, it normally takes about one cycle or 28 days for the birth control to take effect.
