Welcome to Shopify Community. My name is Olivia and I work here.
Setting up a subdomain to point to your Shopify store can be done in a few simple clicks. Like root domains, subdomains will have their own DNS settings - which make it possible for them to point elsewhere from your other site.
There's two ways to connect domains through Shopify. These are described in great detail on our domain help doc.
If you experience problems setting up your domain automatically, then try setting it up manually from within your third-party providers admin. If you contact third-party support, then review what to tell your third-party provider.
Log in to the account that you have with your domain provider.
Find your DNS settings. Look for your domain management area, DNS configuration, or similar.
Find the CNAME record in your DNS settings.
Change your subdomain CNAME record to point to
Save the CNAME Record (usually by clicking Save or Add record or similar).
From your Shopify admin, click Online Store, and then click Domains.
Click Connect existing domain.
Enter your subdomain in the text field (for example,
Click Verify connection in your Shopify admin to confirm that your custom domain has been connected to your store.
Once you complete these steps, simply allow 24-48 hours for the domain to reconfigure. If any issues come up, shoot me a reply in our thread and I'd be glad to help.