iPhone Wi-Fi

Without knowing what you’ve tried it’s hard to suggest anything without being redundant. You can start here→If your iPhone, iPad, or iPod touch won’t connect to a Wi-Fi network - Apple Support.

Perhaps if you can answer a few questions it would be easier to provide guidance:

• Can you go to Settings/Wi-Fi and turn it on?
• Does the problem exist with all networks, or one specific network?
• Has it worked in the past, or has it never worked?
• If it’s worked in the past have you change anything with your network or your phone?
• Have you tried restarting your router?
• Does your router have MAC filtering, AKA Access Control, enabled?