Hi,

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To grant users access to selected users in the same community, you would typically create a sharing set if you deselected theCommunity User Visibility checkbox on the Sharing Settings page.
Click Customize --> Communities --> Settings.
In the Sharing Sets related list, click New to create a sharing set, or click Edit next to an existing sharing set.
In the Sharing Set Edit page, fill in the Label and Sharing Set Name fields. Label is the sharing set label as it appears on the user interface. Sharing Set Name is the unique name used by the API.
Enter a description.
Select the profiles of the users to whom you want to provide access.
Select the objects you want to grant access to.

The Available Objects list excludes:

Objects with an organization-wide sharing setting of Public Read/Write
Custom objects that don’t have an account or contact lookup field
In the Configure Access section, click Set Up or Edit next to an object name to configure access for the selected profiles, or clickDel to remove access settings for an object.
Grant access based on an account or contact lookup:Select a value in the User drop-down list to determine the account or contact lookup on the user.
Select the a value in the Target Object field to determine the account or contact lookup on the target object.

For example, to grant access to all cases associated with an account identified on the user’s contact record, selectContact.Account and Account respectively.
Choose an access level of Read Only or Read/Write. (If the object’s organization-wide sharing setting is Public Read Only, then only Read/Write is available.)
Click Update, then click Save.