You can share reference(s) with other Mendeley users by 12 steps:

Steps 1-2: Open the mendeley.com (1) > click Sign In (2).

Step 3: Enter your email address and click Continue (3).

Steps 4-5: Enter your Password (4) > click Sign in (5).

Step 6: Click on My Library (6).

Steps 7-8: In the Groups section, bottom-left of the page, create a new group or use an existing one > click on three dot icon, which is near any group (7) > Manage Group (8).

Steps 9-10-11: Click on Invite members (9) > enter emails (10) > Send invites (11).

Step 12: Drag and drop references into the group (12) to share. Changes sync with Mendeley Web. Sharing is completed.