01) Access the Control Panel
02) After login click on Layout >> Select template Active >> Click on the EDIT button
Select in the line: Left Side Menu Type
After clicking on the UPDATE button
03) You can also configure it in the Control Panel >> Configuration >> Categories and Subcategories Settings >> Full Categories and Sub-Categories or Drop Down Categories
04) You can customize the source code of the menu as desired by the Control Panel >> Layout >> File Management >> open the includes / boxes folder >> edit the files named categories.
Check the templates folder for the selected layout edit the file column_left.php to check which file to edit the menu on the left side according to the option selected in the Control Panel.