Your lecturer should've given you details about the policy for the exam. My understanding is that there're two possibilities:
The first is a simple take-home exam. You're free to take the exam whenever you want, wherever you want, but you must still conform to rules such as time to finish, no outside assistance, and so on. This kind of take-home exam operates by honor code. If you're unsure you'll be able to stop yourself from cheating, you can take it with other students and monitor each other.
The other is an open book exam. In this case no holds are barred (aside from outside assistance). You can use Google, look it up in textbooks, etc. Open book exams tend to be harder because simple questions will have easily Google-able answers and therefore mean nothing.
tl; dr: ask your professor for details.