Where do I get a passcode

A passcode for what?

If you forgot the passcode on your iPhone, or your iPhone is disabled or unavailable -

Click on the link for instructions on how to reset your passcode without a computer if you have iOS 15.2 or higher.

How to remove your iPhone, iPad, or iPod touch passcode without a computer - Apple Support

Click on the link for instructions on how to reset your passcode using a computer.

If you forgot your iPhone passcode - Apple Support

Are you saying that you forgot your passcode.....or.....you have not set up a passcode on your iPhone and need to do so?