Hello,
First of all thanks for choosing our Theme, we are glad to be you in the WoodMart WordPress family :).
1) If you want to add more categories in the Browse Categories Dropdown then Go to Appearance >> Menus >> Edit Categories Menu and add items to it.
Screenshot for Clarification: https://prnt.sc/12o1ulz
2) To add links to the submenu items you need to Edit the HTML blocks used as the Dropdown menu for the Specific menu item from Appearance >> Menus.
Best Regards