Plan everything out. What sessions happen when, which do you want to do, book them in advance if you can.
Look at the campus tour films for that Uni on YouTube so you feel familiar with the look/layout of the Uni. There will also be a campus map on the Uni website.
If you feel overwhelmed with noise/busy while you are there, just take some time out and sit quietly somewhere for a while.
Take Mum/Dad or someone else you trust with you - they will understand the situations you find difficult.