If you want to share your references, you will need to create a group. The free version of Mendeley allows for one group with only 3 members. All members will need to have their own Mendeley account in order to view the shared references. If you need multiple groups with more than 3 members, you will need to upgrade to a Team Account for a monthly fee.
From Mendeley Web:
Click Create Group.
Then select Public or Private. If you select Public, you need to choose whether it is open or invite only.