To keep track of topics/threads you have not posted in, you will need to click "Watch" button.
Step 1: Open the thread/topic you wish to follow and Click on the gray eye icon found above the topic/thread name.
Step 2: To find your "Watched Topics",
Click on your profile picture in the top right corner of the forum.
A drop down menu will open
Select My Watched Topics
Step 3: "My Watched Topics" will take you to a list of any topics you have opted to "Watch"