Pairing new watch

Setting up a new phone is really easy. Just follow Apple's guide in

Set up your Apple Watch - Apple Support

Hint: Basic (simple) setup is probably less than about 30-40 minutes in most cases. If you are migrating from a previous setup, it might take longer depending how fast the data transfers. Don't start the process at a time when you might want to be up and away, unless you can safely leave the watch and iPhone to work unattended until you return.