Congratulations on your new friend! Here are some tips to make everything go smoothly:
First of all, turtles are reptiles. Reptiles have different needs than dogs, cats, hamster, and other warm blooded companion animals. Reptiles are cold blooded animals. That means they cannot regulate their own body temperature, the way warm blooded animals can. Therefore it's vital that you pay proper attention to your friend's home.
There is an important consideration with your turtle's housing: indoors or out? There are good points to either choice. An outdoor home (if seasonally appropriate) can provide a healthier and more natural environment and that's great for your friend's quality of life. But there are safety risks to an outdoor home - cold, predators, and other threats are very real. Properly set up, an indoor home can be much safer for your friend, but there are important things to think about here as well. The area should be large enough for your turtle to get enough exercise. A sedentary life is not healthy for anyone.
Personally, I prefer a combination of the two types of housing. This provides the greatest benefits coupled with the greatest safety. During the warm months (and warm days in the cold months) all my turtles and tortoises spend most of their time outdoors. Everyone comes indoors at night, and at other times when I'm not able to adequately supervise them.

