If you got your SIM card while in your home country, you'll want to sign up for Mint Mobile and create an account before you arrive in the U.S. After signing up and selecting a plan, you'll get your U.S. phone number while in your home country. If you will not be needing or using your SIM card immediately, you'll select "Activate later" after setting up your account. Then, when you're heading to university, you'll bring your SIM card, put it in your phone, and activate your plan when you get to the U.S. so you can start using your mobile phone service immediately.