You can assign the Guest role to any registered user.
Log in to the Community Administration and click on the Community Users tab.
Click the Guests link in the side navigation bar.
The Guests page opens.
Click the add individuals link in the side navigation panel.
A page listing all community guests opens.
Use the search form to locate the individual you want to add to the community.
Check the box next to the new guest’s name and click Add Selected.
The individual is now a Community Guest.
You can also add all the members of an organization as members using the Guest Organizations link:
Click Guest Organizations in the side navigation panel.
Click add organizations.
Check the box next to the names of the organizations you want to add and click AddSelected.
Each of the individuals in the organizations you selected is now a community guest.
