how can i fix it iphone

As Sherman said, "Use the cord that came with your phone to connect it to the computer." Then follow the instructions in this link...

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

This is the correct link. The previous link is incorrect. Its not a passcode issue

Sync your iPhone, iPad, or iPod using your computer

Learn how to sync music, movies, and more using your Mac or PC.

https://support.apple.com/en-us/HT201253

Use the USB cable that was included in your factory sealed box to connect your iPhone to your computer.

Since he wants to 'fix' iPhone, I assumed that it might be disabled, hence that link. You may be right though.