Publishing add-ons allows them to be used by other users. While a few add-ons have been made available in the G Suite Marketplace for users to install, it is not currently possible to publish your own add-on to the Marketplace.
If you'd like your add-on to be considered for publication, please fill out this form to be notified as we begin accepting additional listings.
In the meantime, you can install add-ons you have developed to test them. You can also install add-ons created by other users in your domain if they give you the add-on's deployment ID.