my printer doesn't work how can I install the printer again or change password

Hi,

Any information about the printer model?

For use with the iPhone, an AirPrint-enabled model (About AirPrint - Apple Support) is needed. The printer and the iPhone must be connected to the same Wi-Fi network (router). For a non-AirPrint model, a special app from the printer manufacturer may be used (with some Wi-Fi printers).

Use AirPrint to print from your iPhone, iPad, or iPod touch - Apple Support

If the configuration is correct, but it is still not working, try the following procedure: Power off the router, the printer, the iPhone, and all other devices/computers. Wait two to three minutes. Power on the router. Wait two to three minutes. Power on the printer. Wait a minute or two. Power on the iPhone. Finally, power on all other devices/computers.