Entity Security controls which workgroups can see which entities in all CRM grids. To Access Entity Security you can open the Security tab and press the Entity Security button. When you press the Entity Security button, the following grid will appear:
In order to change entity security you first need to find the entity in this list, you can do this by using any of the standard search functions. Once you have located the desired entity you can right click on the entity and press the Set Security option, doing this will display the following screen:
This screen is exactly the same as any other assigning workgroups screen, where you can select a workgroup on the left and press the add button to grant that group access to the entity, and you can select a workgroup on the right and press the remove button to remove access to the entity.