The optimum image sizes are displayed in the Prices & Edit screen for each product in the app.
You can also find them in the Products catalogue on our website.
When creating products in the Shopify app, the resolution meter should give you an indication of how the artwork will translate to print.
It’s easy to replace the artwork with a different file if you need to - just use the Replace Image button in the toolbar.
You can also download product specific artwork templates for the most precise results.