How do I make text fields longer?

[Jon <jonjermey optusnet com au>]

Sorry if this sounds like a really stupid question, but I can't find an
answer anywhere in the help or online. How do I make text fields longer
in a Glom Details form? I can see from the Music template, for instance, 
that
the Comments field is longer than the standard, but I can't find any way
to change the size of a field. Am I missing something really obvious?

Thanks,

Jon.