How do i go down to next line?

I have just been introduced to feed the beast, and decided to play around with computercraft, however I have no idea how to go down to the next line while writing code. Ihave treid tab, enter and arrows keys

Split into new topic.

Are you using the edit program or the Lua prompt?

He's probably using the prompt. Otherwise enter would have worked.
Try typing "edit 'programname'" into the interface (outside of LUA) and write the program there.