Hi jiahaifeng81,
Thanks for reaching to us and take our apologies for the long delay in answering.
Navigate to WoodMart > Header builder > edit default header (highlighted star icon) or you can go through admin bar directly https://prnt.sc/Ct9ehRDvvDV9.
Switch to Mobile tab, hover on Mobile menu element, click on Pencil icon and scroll down to Category section > enable Show categories menu option
and choose the categories menu https://prnt.sc/lWIYHQPI8jin
And set categories menu in Appearance > Menus as Mobile Menu.
Please refer to documentation for more details https://xtemos.com/docs-topic/create-mega-menu/
Regards,