I need ko update my phone

Update your iPhone, iPad, or iPod touch

• If you have an iPhone 5S or 6/6plus, the highest you can update to is 12.5.7

• If you have an iPhone 6S through 7, or SE 1st generation, you can update to 15.7.8

• If you have an iPhone 8 or higher, or SE 2nd or 3rd generation,you can update to 16.6

Go to Settings > General > Software Update.

This link will show you how to update your iPhone, iPad, or iPod touch using WiFi -

Update your iPhone or iPad - Apple Support

This link will show you how to update using your computer -

Update iOS on iPhone - Apple Support

What phone do you have? If you cannot update beyond a version already installed, your phone is probably updated to the latest version it can run.

With the limited information you have provided, that is the best answer you will get.

Try doing it though a computer