The person who makes the decision on your PIP claim at the DWP can consider any evidence you send in.
You could keep a diary for a typical day, explaining how your disability affects you, how long it took you to do something and any problems that you. Or someone who knows you, perhaps a relative, friend or carer, could write a letter explaining the problems you have and the help you need. You could ask your doctor or any health professional you see who knows you and your disability for a letter of support to send in with your claim.
All of the above can be considered by the DWP if it helps them understand the difficulties you have with daily living or mobility.