What’s your extender model.
depending on your extender and it’s options you can either set them up to mimic your routers channel names or you can name them independently.
when the mimic the same names your device will roam, if named differently you will have to manually change it. Roaming is dependant on the device mostly unless you have a more complex router that offers a degree of control.
Extenders work by forming a connection to your router so if you have a dead spot with no WiFi you would place the extender between the room with the dead spot and router. Don’t place it in the same room where there is no signal as the extender must be able to communicate with the router. If you do you may have a strong signal to your phone but the throughput will be low to none as the extender struggles to talk with the router.
if your phone refuses to join due to incorrect password you should be able to go into the settings on the phone and delete that profile and then retry adding the correct WiFi password.
