access settings

Hello, 

I had to buy a book for school and I have to use your app to access it. When I had to buy anew computer i was not able to accesss the book. i eventually had to buy the book over again but i am unable to have it download now. i think if i am able to access the settings i will be able to sign out and sign back in. id appriciate if you could get back to me sooner rather than later seeing as i have my midterm next week and am now 2 chapters behind. 

Thanks!