Yes, you can use any of the numerous DL lounges at ATL as long as the DL flight legs are on the same VS booking reference. There's basically a DL lounge in every concourse at ATL.
Your bags will be tagged all the way to your final destination when you check-in, however, when you land at ATL (which is the International concourse or concourse F; map
here), you follow the same procedure as any other arrival in the US. You go through immigration, then collect your bags then go through customs. Instead of existing the terminal you then follow the signs for flight connections, drop you checked luggage off at the bag drop belt and then go through security to reach the departure lounge/concourses.
(If you have TSA Pre - you do need to exit arrivals though and head up to standard departure security where there is a TSA pre lane. There is no TSA-Pre lane in the connecting flights security area at ATL. Staff in the connections area will direct you accordingly if you mention having TSA-Pre)
Once you know which concourse / gate your next DL flight is departing from, head down to the plane train to get to the correct concourse. Once off the train, head up to departures and find your nearest DL lounge. Be warned though DL can and do often switch departure gates / concourses at ATL at the last minute. The plane train at ATL is pretty quick though if you need to change concourses.
You can see from the map above all the concourses at ATL are in a line and the plane train runs through the middle of all of them going back and forwards.
ATL is a very easy and is a very efficient airport to connect through.
. You’re a rare vsitor here these days 