If you're entering the UK on a visa you'll need to collect your Biometric Residence Permit within ten days of arrival. You'll need this card before you enrol on your course and, if required, to register with the police.
A BRP is a card (the size of a bank card) that contains your personal information; details of your unique physical characteristics that can be used to identify you (fingerprints, photograph etc.) and your immigration status and any conditions of your stay.
You must collect your BRP within ten days of arriving in the UK. If you fail to do this within the ten days this could result in your visa being cancelled or a penalty being charged. You'll also need to collect it before your enrolment date, as you must have this to enrol at Kingston University.
If you applied for your visa from overseas, your BRP will be available for collection at the post office. Which post office it has been sent to will be confirmed in your 'decision letter' that you'll receive before you leave for the UK.