No questions are silly questions - if you need to ask - ask.
There is no right or wrong way of doing this, but when I fill in a form on someone's behalf, I always use the third person ie: he, she, it or they., so that it is perfectly clear that the claimant themselves didn't write it. But that's what I choose to do and I know others have done it differently and there has been no different outcome either way.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems