Hi @
welly,
Have you looked at the articles here?
https://devs.x-cart.com/getting_started/how-to-apply-design-changes.html
https://devs.x-cart.com/getting_started/how-to-apply-design-changes.html#registering-template-in-view-list
Basically, you need to create your own template and register it in the ''center" view list with the weight that suits you.
Let me know if it is any help to you.
Tony