Mary
You do not need to use the tick boxes if they do not allow you to answer in the way that you wish, just mark them "see below" and answer in the comments box or attached pages but you must still address the question.
I'm taking your post as it is written not necessarily as it is intended, you won't score for things that you do not do, only things that you cannot do, so you need to explain why you cannot prepare and cook a meal. Be aware they will still consider whether you can complete this activity with the use of suitable aids, so you also need to explain why suitable aids would not allow you to do this, there are a list of aids considered suitable for each PIP activity listed in the PIP Claim guide.
www.benefitsandwork.co.uk/help-for-claimants/pip Gordon