The option to Make Products Visible in your eCommerce store is disabled by default in Dropified settings.
Enabling this option will automatically make the product "available" or visible in your eCom store during the product importing process.
If you only want to do this for a specific product then you can tick the Make Product Visible option in the Extension after clicking More Options when importing a product.
If the product is already imported, you can make the product visible by selecting that option from the bottom part of the Product Edit page in Dropified, then click the green button to update that product.
While using sites like Shopify you may need to update the product availability with the product page of your store as shown here:
For example, you may also need to set that item to your collection/category to make those items appear where you want them to be.
Instructions can be found here: Collections · Shopify Help Center