Site indexing is important for your site's pages to show up in user search results. You can check which pages are already indexed using Google Search Console and Serpstat's URL indexing inspection tool.
If you need to index additional pages, submit an index request using Google Search Console. Go to the tool, then select the resource type, confirm that you are the owner of the site and add a list of URLs for indexing.
The scanning and indexing process may take some time. Google’s knowledge base does not report how long exactly, however, if your request is not processed for a long time, there is the ability to resubmit the indexing request.