By clicking on settings (⚙️) below the cover image on the left, and selecting "Publish Settings":

From this screen you can:

1. Change the Guide access from private to public. IMPORTANT: Changing the guide to public will allow anyone with the link to access the guide and add it to their Spaces. Once made public, anyone can access the guide if they have the URL or it is published in a public space.

2. Change the primary Space. While a Guide can appear in multiple spaces, each Guide has 1 origin Space. Click on the Space name after "Originally published in" to change the primary space. NOTE: the guide must already be part of the space you are changing it to.

3. Change owner of the Guide. The new owner will need to already be an admin or a member of the Guide, and/or member /admin of the origin Space of the Guide.