I need to enter my WiFi password, which consists of letters and numbers but the OTT remote only has numbers.

SOURCE: my blackberry phone lock is on and it asks me to

dont worry it happens some times when you cant remember the passwod of your phone. do one thing type any wong password on your blackberry phone 10 times. after each 2 or 3 times its showes type blackberry just do whatever it says and after 10 tryed it will auto wipe all the codes then it wants new password and you can put your new password.

SOURCE: Keyboard letters wont work but only top row Of numbers

On a notebook computer, there is a FN key that when pressed with the appropriate special function key will disable the normal keyboard and enable the alternate letters (printed in a different color) on your keyboard.
Unfortunately, I can't remember which special function key that is--but the icon on it should give you a clue.

SOURCE: checksum validation failed for the PIN entered on Lenovo password for internet set up

OK, if you have a Password, why are you entering a PIN? They are two different ways of authenticating you as a valid user. You should not select the option to use a PIN. Use your Password or Network Key.

SOURCE: cant enter letters for wifi password

you have chosen the encryption option WEP instead of WPA/WPA2.
go back one screen and change that and you'll be able to enter letters.

SOURCE: Lost password

Enter the settings page on the modem and change the Wi-Fi password to something you won't forget, use a daft sentence like 'my cat wears wellingtons' so you will remember it.