Sharing a Collection works exactly like sharing a Markup, details about which can be found here.
There are a few key differences, however.
First, a Collection will only be visible to those people with whom you share it.
Second, when you share a Collection you’re not only making that particular set of titles visible, but you’re sharing any markup notes you’ve added to the Collection as well.
Whether you share your Collection with colleagues or with accounts, they’ll receive notification in their Notifications widget on their homepage that it’s been shared with them. They’ll also receive an email, should you choose to send them one.
To share, view the Collection, and click into Shares in the blue bar at the bottom of the screen. Again, details about sharing can be found here.