WiFi difficulties

Forigve my wail of frustration. I am old but not monumentally stupid. I have been given my sisters old iphone as she has upgraded. But even though I have somehow managed to get an apple id and to reset the phone back to factory settings myself, I have not been able to connect to wifi in my own home despite having correct password as printed on bottom of wifi modem. I have been unable to connecgt to wifi even before I did factory reset. I have somehow managed to put name of my wifi into this Apple i phone 6S , because it did not automatically see it, but it keeps telling me I have not got the correct password. But I have! It was printed on the bottom of the modem. So frustrating. Been hours setting this phone up. So difficult. I have reset networks twice. I also a neighbours wifi name which appears first above mine, and there is no "Forget this network" option when I tap it or the blue i within a circle. I am going crazy and have bought chargers and everything and been down a shop to get the nano sim sorted and telephone numbers transferred from my old Nokia. I want to go back to my old Nokia 'burner".