To open your store on a custom domain, for example myshop.ua, you need to point the domain to the Shopcore server IP address using DNS records.
The usual option is to add A records in your domain registrar panel. If your registrar only allows changing NS servers, connect the domain to Cloudflare first and create the A records there.
The IP address for your store is shown during onboarding or in the store settings under My domain. After DNS changes are saved, wait for propagation, open the domain in a browser, and make sure the site works over HTTPS without SSL errors.