cannot connect i phone to wi fi but my desktop is connected

It does not appear that you have a question about one of the Apple routers displayed below.....which we support in this forum....but we will try to help get you started.

Please see this Apple support document for more information on how to solve this issue:

If your iPhone, iPad, or iPod touch won’t connect to a Wi-Fi network - Apple Support

If you are still having difficulty after you work through the Apple troubleshooting guide, you will receive faster and more prompt information about your issue if you post in the iPhone support forum, which is linked for your convenience just below:

Using iPhone

Please give this Apple Support article a try. If this still doesn't help you may have better luck getting a possible solution if you re-post your issue to the iPhone area of the Apple Support Communities.