Of course! This is your home! We would advise that you speak to your flat mates first if you are having someone stay over. By the contract, you are permitted a guest 3 nights in any one week.
You do not need to do anything if you are having a guest over unless they have a car, in this case you just need to pop to reception to get a temporary parking permit (free of charge) so that they can park in the car par - please do not allow your guests to outside the blocks.
Please do not give the flat code out to any guests, and accompany them when you are in the flat as you will be responsible for them whilst they are on site.