I have never visited said dark web market... But i guess you'd either have to buy a pre-written market script, or write one yourself...
You'd probably have to run daemons for each coin you wanted to accept, and use the daemon's json-rpc interface to create deposit addresses and handle withdrawals.
I wouldn't use pre-written market scripts for that purposes. Who knows, how many security breaches are there. If you want to get the most relevant information and news about dark web, and dark market - I can highly recommend you this site called
noirdotnews.com which is maybe one the most reliable resources, where admins re-check everything and give you only the verified facts and detailed description of things, which come from dark web. I could find an article of Dark0de Reborn there, and it's pretty interesting I gotta say.