To add FXS to the metamask you need:
- In the wallet select the desired network and then in the cryptocurrencies section scroll to the bottom - click "Import tokens".
- Copy the smart contract address for Frax (prev. FXS) from the list below.
- Paste into the "Smart Contract Address" field.
- Click the "Add Custom Token" button.
The FXS is available on the 11 blockchain networks. Below is a list of Frax (prev. FXS) smartcontract addresses to add to the metamask: