Yes, include any evidence you have which supports what you are saying. Essentially, you need to consider the Activities and their Descriptors and include anything which demonstrates how you fulfil them. You get just the highest point value for each Activity that you meet the Descriptor for: https://www.citizensadvice.org.uk/Global/Migrated_Documents/adviceguide/pip-9-table-of-activities-descriptors-and-points.pdf
Any other evidence you have which supports your claim you should also include, this could be copy letters from your neurologist, letters from your MS nurse, physiotherapist, anyone else you see who you can ask to write a supporting letter. You can also include photos of any aids you use, I had pictures of my wetroom, showing the shower chair and grab bars and photos of my bedroom showing the bed rail and standing frame to help when I’m getting dressed.
I second Aluns recommendation that you join benefits and work. Their guides for members are excellent. It costs about £20 per year, but it’s worth it.
I actually disagree that you should use examples of your worst day, because if you have to have a face to face assessment, and it’s not your worst day, you will look like you’ve exaggerated everything. But make clear what you are normally capable of and what you are like when things get worse. The key to the Activities is that you should be able to do things ‘reliably, safely and repeatedly’. This means if you can walk 40 metres say, that you can do it again without a lengthy rest. And when you do it again, that you can walk safely and reliably (ie that you’re not at risk of falling).
Take your time with the form, write your answers out, then leave it a couple of days, reread what you’ve written and compare it to the Activities so you can make changes as appropriate.
Best of luck.