You can set up product categories and the corresponding acccessable buyer groups on the function window Data Management > Category Setting.

From the "CATEGORY SETTING" window, you can map the PRODUCT CATEGORIES to the suitable buyer group in the Buyer group listing on the center window.

To conduct the mapping; first select the Buyer Group you wish to edit their Product Category options. Once you click and highlight the Buyer Group, move your mouse pointer to the product (MAIN) category, and hold the left button of your mouse. Drag the selected Product Category to the center bottom window under Attribute Setting and place into Product Category folder.

After you release the left button of your mouse, this product (MAIN) category will be categorized to this particular Buyer Group.