There are two separate parts of a custom product template for subproducts: defining how subproducts will look, and setting where subproducts will be displayed in the current template.
At the top of your custom product template -- before the [-- DEFINE PRODUCT --] tag -- you must put a [-- DEFINE SUBPRODUCT --] section to define how subproducts will look. This includes what product attributes will be displayed (name, price, etc.) and the layout of those attributes.
As a general rule, if a product has subproducts, most of the information for the main product is not displayed. You can stick to this rule or ignore it, but the built-in ShopSite templates only display a product's name, graphic and description if it has subproducts. You can use an IF tag to test whether a product has subproducts.
Placing subproducts in your product template is done with a loop::
[-- LOOP SUBPRODUCTS --]
<br>[-- SUBPRODUCTS --]
[-- END_LOOP SUBPRODUCTS --]
This example defines the subproduct to display the subproduct name, price, and an Add to Cart button. It does not display sale prices or alternate currency prices for subproducts. In the product definition, there is a test for whether a product has subproducts, and if it does, only the product name, graphic and description are displayed before the subproducts.