1. If you can't locate the nearby WiFi on your screen, then you can move your cellphone closer to the router or hotspot. When you use a personal WiFi, make sure the WiFi router is connected to power and turned on. If the WiFi is configured as "closed" or "private", it will not broadcast the network name to the WiFi devices. So when you join a "closed" or "private" network, first tap Setting > WiFi > Other and then, enter the WiFi network name, security and password. If the signal is low or intermittent after you join the network, then you may move closer to the router or hotspot, and check if there is anything that blocks the signal and remove it.
2. Sometimes, even though you are connected, you are still unable to access the Internet. Under this situation, you may configure the settings of the network, including DNS, IP address and Search Domain settings. You can reset the settings, including the password of this WiFi network by using "Forget this Network"; and then, use "Renew Lease" to acquire information including the new DNS, IP address and Search Domain from the WiFi network.
3. After trying the above measures, if you still can't join the WiFi or access the Internet while connected, then you can try the following: (1). Restart your device; (2). Reset the network settings; (3). By all means you still experience issues, then considering turning off the WiFi and using your cellular data connection.