For each separately rentable 'bed' you need to make a separate listing on your profile with names reflecting bunk bed 1, 2, 3, 4.
I would also make the title clearer to reflect that it is more of a hostel situation.
Another thing you will have to figure out is how to determine if you rent out to all sexes simultaneously.
And then make it Super Clear in the listings or you'll end up having tons of misunderstandings. Guests don't read listings properly which is why you'd be wise to communicate with guests beforehand to see if they know which situation they are booking into.