Zits are apart of the gift.... Sadly! Just make sure you wash you face and body really good during you cycle. You can use acne medication to treat it. You can't really prevent them, but just wash you face super super good maybe before your cycle.
The zits are just part of your hormones acting up at that time :/ every girl pretty much gets zigs when they're about to have their period. Just wash your face twice a day with soap. Keep in mind that not all face cleansers work for everyone. Find a good brand and make sure it works for you