http://j5kv55yiu3rneydqn4f35kyhejbq3fhkkm7glg5nbtvxgaxthou7g2ad.onion/start-here.html
In Hush Line Settings, in the Email & Encryption tab, paste the key into the text area with the label "Or, Add Your Public PGP Key Manually." Finally, with Hush Line open and your active, visible tab, select "+ Authorize this domain" from the Mailvelope browser extension menu.