How do make other items included in SET show up in product info

[Guest]

Hi OSC'ers!

 

some of my products belongs to a SET (matching design, colors, fabric, etc). how do i make it like this

computer store http://shop4.outpost.com/product/4659048

 

customers can add a product to cart and also include the items that the customer marked checked on a "matching products / set items" selection box.

 

i tried searching for DAYS now for similar functionality but i may be using the wrong keywords on my searches.

 

Please advice/point me to the right direction. Thank you in advance for your help