After your account has been set up, you can begin importing subscribers to communicate with.
After logging into Engage, you can upload subscribers to new or existing Lists, or directly into your subscriber pool without attaching them to a List.
Subscriber lists can be imported in multiple file formats, as detailed here.
After being added to Engage, you can include subscribers on a send within a campaign by selecting a List to pull subscribers from, or by segmentation.
Note that some email addresses are automatically excluded from import to prevent sending to addresses of types that may see emails as spam. This includes email addresses that may represent entire departments, or groups, such as "abuse@" and "webmaster@".