The mansion has two floors (yes, I know mansions only have one, but this is a Kenyan mansion). The second floor has all the guests' rooms, and the first floor contains five rooms: the study (where the golden cashew safely sat in a safe... pun intend), the bathroom (right next to the study), the kitchen, the dining room, and the foyer (where the stairs are that lead to the second floor).
When you enter a room, there will be a description (much like this one) and in the description you may find links that allow you to investigave further. My best advice is click around as much as possible, and a pencil and piece of paper may come in handy.
Apart from snooping about, interrogations and character biographies have already been neatly organized for you. You can find them at the bottom of every page, for a quick reference. And when you think you're ready to guess the criminal, click on the "It's Time" link down at the bottom.
Good Luck!