Go to the Dashboard, select the asset position you are willing to close. Then your position will be closed once the transaction is completed.
Eg. Close a Long $DOGE Position. Basic logic is sell your $DOGE to repay your loan. (You can always refer to your Dashboard to see your in-debt asset.)
Select the amount of $DOGE you want to sell.
Use the sold $DOGE asset to buy BUSD. (If your in-debt asset is BUSD)
Pay the gas fee and once the transaction is completed, your position is successfully closed.