Not too hard;

Spoiler:


1. Select hotel, should load with a calender
2. Click the little box on the 17
3. Enter number of rooms and number of guests (must match whats in the title i.e. you can't book 1 person), currently only for the 17th & 18th, Click the button with the arrow
4. Loads with prices on the next screen, click the button with the arrow
5. Enter in an ID & Password and click the button under the blue underlined text
6. Enter in name, address, phone etc so they can confirm your booking

I'm still looking into single accommodation, but I think that's how you book for two or more people.