To enable server side rendering for Shopify stores, you must have the Shopify Bablic App installed on your Shopify store.
That's it. Once the app is installed it will take care of everything for you.
How does this work
The app uses the Shopify Proxy API to route some requests via Bablic servers.
According to the Shopify Proxy limits, the translated URLs are generated on the sub-directories /a/lang/<language-code>
For example: if this is your website: https://website.com/
The translated URL for the homepage in Spanish will be: https://website.com/a/lang/es/
This is the URL that search engines will index, but If you'll open that link in the browser it will show as https://website.com/?locale=es.
You should submit your translated sitemap to Google Search console. For the example above the sitemap for Spanish will be:
https://website.com/a/lang/es/sitemap.xml