my iPhone is saying that it is unavailable what do I do to get in

You can sometimes remedy this without a computer if on iOS 15.2 or later by tapping on "erase iPhone" , but you will still need the Apple ID password. It will WIPE the phone, no choice!

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

video

https://youtu.be/7s8-zLG9ySQ

 ios 15.1 and earlier:

If you've forgotten your iPhone passcode – Apple Support (UK)

You will receive the unavailable page after too many attempts in passwords. You must factory reset your device to unlock the device.