1. Navigate to Lists > Manage Lists.
  2. Click the Manage basic and advanced lists block under List Actions. 
  3. Select My Lists
  4. Find the list you want to share, and on the right side, click User Access
  5. Click Add User(s)
  6. Search for User(s) to add
  7. Click Search
  8. Click >> to add the User to the Added Users column
  9. Click Save and Exit