You can use Synthetix.Exchange with MetaMask, Trezor, or Ledger wallets. Simply connect a wallet that holds at least one Synth, and your balance will be displayed, along with the conversion rates.
Converting is as simple as choosing a Synth to convert from and to convert to, and confirming the transaction. Once it has been processed on the blockchain, you’re all done! All conversions are on-chain, and thus generate the standard 0.15% fee for all Synth transactions that are distributed to locked SNX holders.
If you have any more questions, please come join our community on Discord