Adding a file to your OneDrive is easy. Just touch the menu button (three small circles) in the upper right, and you'll get options for adding new items or you can select items you want to share.
As I mentioned before, the app really comes in handy when you have a subscription to Office 365. With the Office app on your iPhone tied to a subscription, you'll be able to open and edit Microsoft Word, PowerPoint, and Excel documents from your iPhone. You'll only be able to make basic edits within the Office app and it's a little annoying to have to open a separate app to edit, but I like that it is available.
One omission I noticed in OneDrive is the option to password-protect your documents. I suppose most people probably have a PIN to log in to their smartphones, but that's one feature that Dropbox has, and it's a level of security that was left out of OneDrive.
Backing up photos and videos
OneDrive will also automatically back up the photos in your iPhone library, which is new to the app in this version. Right when you start the app and sign in, OneDrive starts backing up the photos on your iPhone. Depending on how many photos you have stored on your phone this can take some time, but when it's finished you'll be able to browse your photos easily, swiping to advance to the next picture, just as you would in the iPhone library. It also means that you could clear out space on your iPhone, but that would be true for any of the big cloud storage apps.
The one thing I don't like about the photo backup feature is that it starts automatically. The app has the backup photo setting on by default, and you'll need to open the settings to stop the automatic upload, but photos already uploaded will stay on your OneDrive (until you delete them). I think it would be better to ask me in the beginning if I want to back up my photo library rather than assume I do.