[NTG-context] Third party modules in LMTX

I would like to use Wolfgang's t-letter module, but need some help. I found the following instructions: "The ConTeXt suite only comes with Taco's t-bib module. If you want to install a new module, say Wolfgang's t-letter module, you can use first-setup.sh --modules="t-letter" BUT, the LMTX standalone does not have any "first-setup.sh" shell script. Is there another way to install the "t-letter" module for use with LMTX? Any help is appreciated. Thanks Darel