reMarkable has an onscreen keyboard that appears when you are required to type in information. In Keyboard Settings you can find your default keyboard, which will be indicated by a white dot. Tap the language currently displayed to change to another available keyboard.
Tap the number key 123 to enter numbers or symbols, and tap the += key to get more symbols. Tap the letter key abc to return to the regular keyboard. Tap the shift key to activate uppercase letters.