How to set up a homepage when all others are proxied

I have a Samcart account for online selling. I use their service by proxie.

I just purchased a new domain. I need to set up a www (home) page for my new domain,

All other pages for that domain will be proxied to Samcart.

What should I do next?

1 - I have another website called Is it possible to create a www redirect to my home page?

2 - or do I have to have a physical Expressive-views website?

3 - and if I have a physical website, would I set it up here? Or?