.... from a different page on the site to a different category.

In other words I have 3 pages on the site dealing with 3 separate ways of getting/buying products (retail, free samples, promo item branding). They obviously deal with 3 different categories of products (retail, free samples, promo items).

I have the categories done in zencart and the right products in the respective categories, but how can I link a BUY button on the retail page to go directly to the retail category and its items, the BUY button on free samples to go to the free samples category and the promo item branding to the promo items category

Thanks!