You can create groups for collaboration in Mendeley Reference Manager to share references in. This can be done quite easily in Mendeley Reference Manager itself.
On the left menu, under Groups, you can create a new Group by clicking on New Group and entering the name of your Group.
You can edit and invite members to your Group by clicking on the 3 dots next to any Group name and clicking on Manage Group. You can then invite up to 24 members with Mendeley accounts.