Add Unmatched source data from DataMesh

I am using DataMesh to update a staff file each month. The source sheet contains the names of all staff - some of whom are new and are not in the target sheet. The Target sheet also contains the names of all staff but also has the names of terminated staff not listed in the source file. I would like to add the new staff from the source sheet to the target sheet (I think these are labeled as unmatched) how do I do this?