AFAIK, there is no user manual for an individual lathe model that was made by Atlas, as your lathe was.
I think what you might be looking for is the Manual of Lathe Operation which is otherwise known as MOLO. I am not an expert on the MOLO ... I think our resident expert is Robert (wa5cab), and he wrote a history of the MOLO that you can find here:
History of the MOLO. The MOLO is not model-specific but contains info for all the lathes in production at the time it was printed. Someone correct me if I am wrong, but I think that the MOLO for the Craftsman lathes that were manufactured by Atlas is the same as the Atlas version except that it says Craftsman on the front. Or at least very similar. Many, if not all, the lathes pictured in the Craftsman MOLO have Atlas badges. So to get started I think you could use one of the Atlas MOLO versions on our site here:
Atlas MOLO's.
Here is a link to the 1968 version of the Craftsman MOLO on the Vintage Machinery website:
Craftsman 1968 MOLO. As far as I can tell it is the same as the Atlas version from that period.
If you want a hard copy, Craftsman MOLO's can be found on eBay and Amazon, and other sites that sell old stuff. Robert can help you figure out approximately when your lathe was made by the serial number (and other clues) if you don't already know.