You will need to be signed into your Office 365 account to edit the document and save it directly back to Sync (recommended).

The document will open within the Microsoft app.

Tap Open at the bottom right corner of the screen.

Open and edit with Microsoft Office mobile on Android

When you tap the back arrow in the Microsoft toolbar, your edits will be saved directly to Sync and be available on other connected devices, as well as the Web Panel.

You will need to be signed into your Office 365 account to edit the document and save it directly back to Sync.

Browse through your Sync account and tap the document.

If Sync is not listed as an option, tap the Ellipses Icon (…), tap Edit on iPhone (or Edit Sidebar on iPad), then tap Done to enable Sync.

Tap Browse (top left corner of the window).Tap the folder icon on the left side of your screen (iPad) or the bottom of the screen (iPhone).Open the Microsoft Word or Excel mobile app.Open and edit with Microsoft Office mobile on iOS Open and edit with Microsoft Office mobile on Android.Open and edit with Microsoft Office mobile on iOS (iPad and iPhone).You can open and edit your documents and files stored in Sync, directly from these apps (editing requires an Office 365 subscription). Microsoft provides a full suite of mobile apps for iPhone, iPad and Android devices, including Word, Excel and Powerpoint. Using the Microsoft Office mobile apps for iOS and Android with Sync

How to sync office 365 with documents