ApiDrop has a sophisticated importing method that permits you to match supplier's categories with your store ones.
To define in which category your supplier's products will be imported, open your platform's settings page and click on the "Categories" tab.
On the left column, are listed the supplier's categories and on the right column you can choose your matching categories.
Once a category is matched, ApiDrop knows were you place your products during next import.
Matches can be changed every time you want so if a product has been already synced and you want to sync it again to place it in the right category, you must use the "Force Sync All" (massively) or the "Force Sync" (single) option in the "My Store" list. This function will replace EVERY information previously modified about that/those products you are syncing again.