You can see who has access to your guide by clicking on the guide settings (⚙️) below the cover image on the left, and then selecting members:

From this page you can:

1. Invite people, and give them authority to edit (by clicking on "invite to edit" even in draft mode. Enter a person's name or email address, once you click on "invite" they will be notified by email with a link to the Guide.
2. Give editing permission to people that are already subscribed to the guide (by clicking on "make admin")