Backlinks Indexing   SUBMIT

Hi there, I recently got involved with a WP based media company that creates great, fresh content but seems to be lacking a proper online presence. Its not getting indexed properly by google and using Moz's backlink feature, it is apparent that it is lacking in proper SEO. I have started doing things like optimizing images and adding proper image tags and such but how do I go about increasing ranking and building backlinks? The platform already has 4000+ articles but nobody was paying attention to SEO before I came on board. We do have Yoast running but I am not sure how good that is. Other than that, I have been working towards increasing page speed and such. Is there any advice you would like to give? Thanks!