The content in dynamic pages can change each time the page is displayed, and you are going to want SEO to index that page for any of the content it could display. The SEO settings for dynamic pages let you control how your pages are indexed, and they let you reference the data in your collections for indexing.
To get to the SEO settings, go to the page settings for a dynamic page and click the SEO tab. You'll see five sections there:
What's the page's title in search engines?
What's the page about? (Page Description)
What are the page's keywords?
Which image do you want to share on social?
Hide this page from search results?
In each of these sections you can use content from your collection so that the dynamic content for the page is used for SEO.
A search engine preview is displayed at the bottom of the pane that shows how the fields you selected and the description you added affect your page's SEO.
See this article for a full description of the SEO settings tab.