I, too, retrieved RXVSAM from
www.cbttape.org, "file" 268. This will give you a .ZIP file on your PC. After you extract the contents of the ZIP file on your PC you will have one file, FILE268.XMI.
I then sent FILE268.XMI to a mainframe, and used the RECEIVE (RECEIVE INDATASET(FILE268.XMI) command to extract its contents. This creates a source type PDS; you will discover its name when you receive it.
Even by CBT standards the documentation in the source PDS is lousy. Its very verbose and poorly organized. You assemble one large member in the PDS, RXVSAM, and use the binder to create a load module from the object code. Fortunately there are no unusual macro libraries for the assembly, or SYSLIBs for the link edit step. The assembly requires both SYS1.MODGEN and SYS1.MACLIB. You then make this load module library available to your TSO session using the TSOLIB command as Mr, Prins suggested, or if you run TSO in batch you can use STEPLIB, again as Mr. Prins suggested.
Good luck with it.