You can to login at certain Darknet marketplaces with the only help of urls, this determines next : upcoming vendees and vendors can't register before they will obtain an alternative link from an already registered shopper.
Search for those at http://deeponionmarkets.com/, it posts new links to concerning Deep Web markets. You shall go to these links in order to sign up at the sites.
In case that there are some problems with an access,for example, links won’t work, you should lie in wait and check for Deepweb marketplaces links. Keep trying, as long as some of the marketplaces shut down and launch signing up from time to time, due to server load.