You are required to log into some amount of Darknet markets with the only help of alternative links, which means a tricky situation : prospective vendees and dealers lack the ability to enroll before they will get an alternative URL from an previously joined vendor or buyer.
You can find those at http://deeponionmarkets.com/, it posts active urls to described Deepweb marketplaces. You shall follow these urls to get access to the sites.
Whenever there are some troubles with an access (links don't work), you should hang around and check for Deep Web markets alternative URLs. Carry on, as long as some of the markets may stop and let signing up frequently, due to server load.