Get your SPL tokens; you can turn ERC20 <> SPL at Sollet.io
Go to https://dex.projectserum.com/#/list-new-market to list the market.
The Token Address or Mint Address is the contract address of a token i.e the token identifier, do not send tokens to this address.
Copy the New market address
If anyone wants to trade on the market:
Click the + on the homepage of the DEX
Enter the New market address
So anyone can now list any SPL or (wrapper on) ERC20 token on Serum
Creating a market can cost up to 10-15 SOL