You need an Apple 2 with a Super Serial Card (or an Apple IIc with its built-in serial port).
You need a serial cable connecting the Super Serial Card to COM port 1 on the PC. You also need a valid serial cable (male 25 pin on the PC side, female 9 pin on the PC end). This is a straight through cable.
I presume you have unpacked the PC software in a directory called PROCOMM:
Set everything up. Connect the computers. Boot up on the Apple with a DOS 3.3 disk. Get to the BASIC ] prompt. Type the following:
On the PC, run Procomm.
Within Procomm, type the following:
What have we done? We have told the Apple to expect input from slot 1 (the Super Serial Card and thus the PC). We have set the Super Serial Card for 300 baud (6B) and set the port parameters to match the PC. In Procomm, we set the PC for 300 baud, and sent to file SEND.AP2 to the Apple.
What does SEND.AP2 do? It goes into the Apple monitor, copies about 500 bytes, and then saves the bytes as a Binary file called send.
Boot the disk containing our little file. On the Apple 2, type:
Switch disks. On the PC, type the following: