ERC20 functionality is currently in internal alpha.
Active ETH wallets can be seen on the currency display itself, and can be selected as a linked wallet.
If you do not see an option to switch linked wallets, you do not have an activated ETH wallet yet. Check the Settings -> My Wallets page and wou will find the option to enable it here.
Please note that even if you do activate your ETH wallet, you are not able to use it to store ERC20 tokens - any ERC20 tokens sent to your TenX ETH address will be PERMANENTLY LOST.