Up to 20 themes can be used in your online store. However, only one theme can be published at a time. When someone visits your e-commerce store, they will see your published themes. On your Themes page, the published theme is marked Live Theme.
Step 1:Go to Shopify admin and select Online Store > Themes.
Step 2: Click publish button for the theme that you want to publish.
Your Live Theme will be renamed after the new theme has been published. After that, the old theme will be moved to the page’s Theme Library section.