If you completed the carrier activation steps for AT&T, Sprint, T-Mobile or Verizon when you purchased your new iPhone online, it will arrive ready to use. Just turn it on and follow the onscreen instructions to set it up. If you chose to skip carrier activation at the time of purchase, you’ll need to contact your wireless carrier or visit an Apple Store to enable cellular services. You can also set up your iPhone without a nano-SIM using Wi-Fi. You will need an active nano-SIM to enable cellular services.