Check for an Internet connection
It's best to set up your Mac somewhere that has a Wi-Fi network or other connection to the Internet. Your Mac will use that connection to complete certain setup steps. If the network requires a password, have the password ready.
Plug in only the essential devices
If you're using an external keyboard and trackpad or mouse, turn them on or plug them into your Mac. If you're using an external display, plug it in and turn it on as well, but don't connect any other peripherals yet. And of course plug in your Mac.
If you've never used a trackpad before, here's a tip: To click, press down or tap on the trackpad surface.
Turn on your Mac
Use the setup assistant
A series of windows will ask you for setup details, such as your Apple ID. If you've used iTunes or have an iPhone or iPad, you already have an Apple ID. Use the same Apple ID on your Mac.
We recommend that you let the setup assistant turn on FileVault, iCloud Keychain, and Find My Mac. You can also let it transfer information from another computer or Time Machine backup, or you can do that later using Migration Assistant.
You'll be asked to create the name and password of your computer account. You'll need this information to log in to your Mac, change certain settings, and install software.