The ERC20-type COSS tokens have been replaced with the new ERC223 tokens on the COSS exchange.
If you keep COSS tokens on COSS exchange then you do not have to do anything.
Be careful when buying tokens outside of the exchange (there is the new ERC223 fork and old ERC20 tokens in the market)
COSS token address: 0x9e96604445ec19ffed9a5e8dd7b50a29c899a10c
The new COSS ERC223 was automatically credited to wallets.
If you do not see the two tokens and have held COSS on MEW before the fork, click 'Load all tokens', then click 'Load COSS'.
Etherscan would not be able to show the new COSS tokens until after a tx has been made on the address.
If you store COSS in a wallet outside coss.io like MyEtherWallet, you are required to set up the smart contract identifier again unless you haven't done so after the fork.
Check out the tutorial for instructions: https://coss.io/coss-token-based-fee-split-allocation-tutorial
Learn more about the ERC223 update: