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

1) Click "Connect to Flickr" in the Moment Uploader screen

2) Sign In to your Yahoo account

3) Click "OK, I'll Authorize it" to allow Filepicker (the service Arkiver uses to connect to your online accounts) to access your Flickr files.

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