You never enter text directly into the entry box with S60v5. You have to click on the box you want to type in, which will then bring up the text-entry screen (from here you can pick which entry system you'd want to use; in this case, T9 alphanumeric keypad). There is a small preview box at the top of the screen showing what you want to type, a check mark button at the top, options button at the top, left/right arrow keys, backspace, and the standard number keys.
After you're done typing whatever it is you wanted to type, you have to hit the check mark so that your text gets pasted into the text entry box you were trying to type into in the first place. From there, you can hit the send button.