I need to install iOS

Ios 14 is not available at all. You can only install the current version for the device you have.

If you have an iPhone 6s, 6s plus, 7, or 7 plus, that’s ios 15. If you have an iPhone 8 or newer, that’s ios 16. If you have a 6 or 5s, 12.5.6 is as far as they will go.

Sorry, but that is not possible. However if you provide some basic information, such as device, existing version of iOS, we may be able to assist.