Go to the specific listing under the 'Spot Listing' menu item. Scroll down to ‘Share Listing' and on the far right click 'Share'. Here you will be able to add other users by email address, along with the duration you wish to share the space with them.

The user who wants to share the space can then login to their account with their email and password.
The user who you share the space with will be charged a $1 convenience fee for using the app/Access+