How do I make changes to my ucas application?

I'd like to put on my application that I have a disability but I'm unsure how I go about changing this.

The reason I didn't say that I had a disability to begin with is because my disability is so much a part of me and I just get on with it and I forget/ don't consider it something I need to separately state.

It was only when a teacher sat down with me and used the word disability that it hit me that I did have one and that its effects were noticeable to others and not just myself.

It does hinder me sometimes but I tend to just let it take it course and then when I am out of a rough patch I dedicated time to catching up with work but it does cause me to fall behind with work and deadlines so it is something I need the uni I am going to to be aware about.

Anyway, do I have to contact ucas by email or something to change this? If you can help I would appreciate it.

Thank you in advance!