After a market is closed and resolved, you can claim your earnings using the Polkamarkets web application.
How-to Instructions
Head to the portfolio section, and filter markets by Resolved, on the right-bottom corner:
Claim Market Outcome Winnings
If you hold shares of the winning outcomes, they'll be displayed as available to claim. Click Claim Winnings. You'll be prompted with a Metamask transaction. After the transaction confirmation, your balance will update accordingly.
Withdraw Liquidity
If you added liquidity to a market, you'll be able to claim it back, along with earned transaction fees, in the Liquidity Positions section.
Click Withdraw . You'll be prompted with a Metamask transaction. After the transaction confirmation, your balance will update accordingly.
Claim POLK from Reports
If you placed POLK to report the winning outcome, you'll be able to claim it back in the Report Positions section.
Click Claim. You'll be prompted with a Metamask transaction. After the transaction confirmation, your POLK balance will update accordingly.
Watch the video for a better understanding of how to claim your winnings: