Shopify online stores have SEO built in and also features to help you optimize your content. Some SEO is taken care of automatically: auto-generated canonical tags are added to pages to prevent duplicate content from appearing in search results, your website's sitemap.
You can Bulk Edit view your
-Titles
-Meta Descriptions, and
-URL handle
By selecting your products and selecting "Bulk Edit"
CAUTION with changing URLs as this needs to be strategic by using redirects to keep your link juice and save broken 404 pages being indexed