You can upload any kind of document from your device or from any kind of cloud storage, such as Google Drive. To upload from your computer, either click and drag your document into the large Upload Rectangle or click anywhere inside the Upload Rectangle to access your device's files. To upload a template or from your cloud storage, click on the Other option. You will be given a multiple selections to choose from, including your Templates, Google Drive, DropBox, etc. Your most frequently used docs will also appear to the left of the Other option for easy access.
If you would like to upload another document, scroll below the already uploaded doc and repeat the process; choosing from the Upload Rectangle or the Other option. Once your document is uploaded, you can rename it or add a deal value to it (recommended if it's a sales document). You can then add your recipient(s).