Microgestin is a combined oral contraceptive pill. This means that it has synthetic versions of estrogen and progestin that prevent your body from ovulating. All birth control pills provide sufficient hormones that, if used properly, prevent pregnancy by more than 99%. However most people don't use their pills right (i.e., missing pills, taking them very late, experiencing vomiting or diarrhea which lower its effectiveness). When pills aren't taken properly, you lower your efficacy rate to the "typical use" rate which is about 95% protection against pregnancy.
All you have to do to protect yourself is take your pills around the same time every day. Since your pill is COMBINED, you have a bit of leniency as to when exactly you take it, but trying to take it at the same time (like before you go to bed or right when you wake up) gets you in a good habit of always taking it.
For most first time pill users, many doctors say to wait at least a month to have unprotected sex, as your body may need a chance to get used to the hormones. Some pill packets say you don't have to wait at all, or only wait 7 days, but its a good rule of thumb to let your body adjust.
If you have any other questions feel free to ask