After setting up your Metamask wallet and supplying your address with AVAX, go to https://www.baguette.exchange.
Click on Connect to a wallet.
Choose Metamask and type your password.
Select Avalanche Network and your wallet.
Select the token you want to sell at the top and the token you want to buy at the bottom.
In my example, I want to sell AVAX to buy BAG.
Click on Swap to make the exchange, Metamask will open for you to confirm the operation.
Click on Confirm and wait for a few seconds.