There are a few ways!
Click on People in the left hand navigation menu. This will bring you right to the people directory, where you can click and view all of your team member's profiles!
Or click on the name of the author of a post — you can do this from your feed or from a post page.
Or use the search bar in the lefthand navigation menu to find a specific person you are looking for. Click their profile photo in your search results and you'll be taken straight to their profile.