Just to set up your Office for the first time, visit Office Setup and follow the guidelines on the screen. In case, you purchased the office setup online then, you can directly visit the official site www office com and open my account as to manage your account and other details.
Office.com/Setup has great reputation with great features. In case of scanning app such as one from the best scanner apps available in the iPhone, OneDrive is the best alternative from Microsoft. It does not have as many features as a stand-alone scanner app, but it is good enough for most of the tasks.