Path: Settings > Configuration > Leads > "Agents Required to 'Accept' Leads" checkbox & "Rejected Lead Agent" dropdown. 

By enabling this feature, agents will be required to accept a lead via a link sent to their email before they can view the lead details. If an agentrejects a lead, it will be auto assigned to another agent in the office, whom the admin can set per agent through the "Rejected Lead Agent” dropdown, or sent to the Unassigned Queue for manual reassignment. 

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If this feature is enabled, a new item will appear in the “Leads” drop down entitled “ Pending Acceptance”. This page allows office admins to view a list of pending leads and more easily identify problems with agents claiming leads.