Please login as an Admin, and then click on your profile image on top right and click on Admin Panel.
On the left menu click on Topics. You'll need to first create a few topics by clicking on Add Topic button.
Click on the "..." icon next to the topic that you want to add to the left menu and pick "Add to navigation". After you're done with adding all topics to the navigation refresh the page and go to Home and you should see the topics in the left menu.