What do i have to do to swap a manual transmission to a automatic on a 1993 Chevy 1500 truck?

Since the manual is five speeds and the auto is four, you may have to find a corresponding driveshaft, as the manual transmission has a longer body. Also, unless you're swapping in an older auto transmission, like a 700R4 or a 4L60, 1993 was the gear General Motors went to the electronic 4L60E transmission, which will require the engine ECM to be reflashed and the parameters added to interface with the transmission.