QGIS plugin

Select the Processing tab and the Providers list item. You should find the WhiteboxTools entry there. Select the down arrow, and check the Activate and Log commands output checkboxes. Lastly, enter full file name of the WhiteboxTools executable file contained within the decompressed WhiteboxTools folder that you downloaded previously (see note above). If you are using a Mac or Linux computer, note that this may require you to 1) select a file contained in the folder that is not the executable (QGIS seems to exclude files without extensions, which the WhiteboxTools executable is on MacOS and Linux) then delete the file extension (see below). You will also need to leave the textbox by selecting any other feature on the dialog box before pressing the OK button.