If you already have ETH/ERC20 activated on your TenX wallet, go to the settings menu, click on "My Wallets" and select the crypto currencies you would like to enable.
If you do not have an ETH wallet yet, do check the My Wallets page from time to time. ETH is currently undergoing staged rollout to the public; if slots are open, the option to activate the ETH wallet will be displayed there. ETH functionality will eventually be extended to all users.
ERC20 is currently in the internal alpha phase; please note that even if you do activate your ETH wallet, you are not advised to use it to store ERC20 tokens.