If you track multiple websites, find "Rank Tracker" at the top of the screen and select "My websites" from the dropdown.

If you track one website only, clicking "Rank Tracker" will be enough.

Choose the website you wish to delete, and click on the three-dot icon ("⋮") on the right-hand side.

Select "Remove".

If you enabled the Compact view, the "Remove" option can be found here:

Once you complete this step, the website will be deleted from your Wincher account.