Hello,
First of all thanks for choosing our Theme, we are glad to be you in the WoodMart WordPress family :-).
I have visited the URL you provided. To add or change the product categories you need to Go to Products >> Categories. And you can add new categories or can change the existing ones.
Screenshot for Clarification: https://ibb.co/kSvPZGt
If you want to add or remove categories from the categories menu then you can edit from Appearance >> Menus >> Categories Menu. And you can configure items according to your requirements.
Screenshot for Clarification: https://ibb.co/4Rbnncx
If you want to ask anything else then provide with some relevant screenshots of the specific area to check it myself and help you out accordingly.
Best Regarding.
.
