To upload a document:
You can also drag and drop files directly into the browser window.
Documents are uploaded into the folder you are currently viewing.
If the document type has a Folder Mapping configured and you upload to the root folder (My Drive), the document will automatically be moved to the mapped folder.

The following file types are supported: PDF and images (PNG, JPG).
XLSX and CSV files are also supported. They behave like any other document type, but are additionally marked as Datasets - making them available for use with Formula Fields.
XLSX and CSV files should follow these guidelines:
Every uploaded document goes through an automated multi-step processing pipeline:
The file has been received and is queued for processing.
Status: PENDING
A fast preliminary scan identifies the document type, title, date, and total amount. These values may be refined in subsequent steps.
Status: PARTIAL
A comprehensive extraction pass analyzes the document according to its document type schema. Formula Fields are also evaluated during this step.
Status: EXTRACTED
The extracted data is indexed so the document becomes searchable.
Status: INDEXED
Each step runs in the background. Processing usually completes within a minute, though it may take longer during periods of high activity.
The Upload app shortcut is available on the Apps screen and can be pinned to the Quick Access Bar for easy access.

The Upload shortcut is simply the Browse app with the upload dialog opened automatically.