To try and rank your collection pages higher in search engines you'll want to manually set the SEO settings. You can control the SEO settings for your collection pages by editing the Title, Description, and URL on your collections. Sometimes you'll want these to be different for search engines, than what your customers see.
Navigate to the collection you want to add SEO for under Content > Collectionsand click Edit. Under the SEO tab set the SEO Title, URL Handle, SEO Description, and any Tags you want.
NOTE: As with all SEO changes, it may take a few days for changes to appear in search engines and when the link is shared.