Tracy
Welcome to the forum, you might want to have a look at the following FAQ which explains where everything is
Welcome to Benefits and Work You can report a Change by writing to the DWP office dealing with your claim but you should be very certain that you will meet the criteria for the Enhanced award before doing so as notifying them of a change in your limitations will result in a full reassessment of your claim and the new Decision that will be made will supersede your existing award, whatever it is.
I assume that you have previously scored fro problems with your walking, to score the 12 points needed to receive an Enhanced award you will need to show that you cannot now reliably walk more than 20m on the majority of days.
Have a look at our PIP Claim guide for more information.
www.benefitsandwork.co.uk/help-for-claimants/pip Gordon