First of all, this function is just for Ethereum wallet, not for Bitcoin wallet. So you should switch the wallet to ETH at first.
On the ETH wallet assets page. Tap "+" button to enter the assets management page.
Now, you can tap “All my assets” to turn on token display in Assets page if this token in your wallet.
Or try add the tokens manually: enter the token name or contract address on the search field and tap the “+” button.
Go back to assets page, there you'll find the token being displayed.
PS: If you cannot find the token when searching, Please click here to submit the information.