To add photos to Arkiver from your Google Drive account, you'll need to connect to Google Drive.  

1) Click "Connect to Google Drive" in the Moment Uploader screen

2) Sign In to Google Drive and click "Accept" to allow Filepicker (the service Arkiver uses to connect to your online accounts) to access your Google Drive files.

4) That's it! You'll be connected to Google Drive and can pick photos to upload to your Arkiver. Hooray!