The Tribute Acknowledgee Link Mapping is included when purchasing the Tribute Data Destinations, but found within the Gift tab. See Tribute Mapping for full details

For the Acknowledgee row – if you would like to select an Individual Relationship as a contact, you would do that in the Default Value column (this does require the purchase of the Individual Relationship data destination in addition to the Tribute data destination). If left blank (as above), the Tribute Acknowledgement will default to the Honor/Memorial Constituent record.