You can edit sharing permissions for contact with access to a property on the Sharing tab:
- Locate the contact whose permissions you'd like to edit in the table.
- In the Action menu on the right, select "Edit Contact's Permissions."
- The Edit Sharing Permissions screen will open. Select the new level of permissions and then click "Edit Permissions" to save those changes.
If you need to set Custom permissions, an additional screen will open allowing you to make more granular selections. Once you've made your selections on that screen, click "Apply Selection." You'll then be taken out to the Edit Sharing Permissions screen, we're you'll need to select "Edit Permissions" to apply all your changes.
For how to edit a Data Exchange share, see: How do I edit a data exchange share?