On the left-rail, you'll see an option to "Explore".
When you click on "Explore", you will see a list of every Company that has a profile on Harvest. Companies are categorized by Firm Type, and each Company has a "Plus sign" that enables you to Follow that Firm (read more about Following). You can view all firms within a particular Firm Type by clicking "See All" on the right side of each row.
By clicking on a Company, you will be brought to that Firm's unique page on Harvest, which has detailed information about the firm and a repository of all of the content that they've contributed to Harvest.
If you see a Company labeled "Exclusive Access", that indicates that their is additional content and features available to you on their Page upon request, if you meet the qualifications set forth by that Company. It is important to update your Profile Settings in order to maximize the amount of content that you can unlock. (Learn more about Exclusive Content here)