To start receiving newsletters in Digest, simply locate your Digest email address by clicking on Newsletters at the top of your account. Copy it. Then subscribe to any newsletter you want with it. Newsletters that you subscribe to will start showing up within the Newsletters page in your Digest account.
If you want to add your newsletters into a new or existing Digest, just click on the Newsletters source button within the Digest builder. This will automatically pull in a list of the newly received newsletters.
The newsletters will now display within your Digest. Clicking on each newsletter title will take you directly to the newsletter reader to read that specific newsletter.