An easy, but dumb, method would be redirecting from the home page to the category page via the .htaccess file.
A better approach would be creating a custom module that makes the home page display a block listing products from your category. It was discussed some time ago:
https://forum.x-cart.com/showthread.php?t=75633
However, in this case you will have to site pages listing the same products - this may be not what you are looking for.