The Home Office requirement is that you must collect your BRP card either within 10 days of arrival in the UK, or the expiry date date of the vignette in your passport (yellow stamp), whichever is later. Your BRP collection location will be stated on either your visa decision letter / email or in your visa application form itself (which you can retrieve by logging in to your visa application account).
If your collection location is a Post Office, you will need to visit the Post Office with your visa decision letter and passport.
If your collection location is the University (usually with ‘Cherry Tree Lodge’ as the delivery address) then please visit this link for information on where and when you can collect your card.