Close a position means to market sell/buy the assets that have been previously bought/sold by the bot for opening the position.
To access your open positions, click on DCA BOTS/POSITIONS in the main navbar or visit this page.
By clicking the "Settings" button on the right of the specific open position, you can access the edit position functionality.
The following modal is rendered. Click on the small arrow next to "CLOSE POSITION".
By clicking the "CLOSE" button, you will send a manual command to close the position.
This action can take from a couple of seconds to minutes, depending on the type of pair, exchange, liquidity, and many other factors.