You can do this anywhere you can find information about the user.
Preview the profile
If you hover your mouse over a username, a small window opens with content from the user's profile.
You will see several icons
Click on the Plus + icon titled “User” you will find the “Follow” option
Member List
Go to the Member List you will see the user profile panel with the icons. Select the Plus + icon to follow
How to UnFollow
Do the same steps as you would to follow the user.
If you are following them you will see a Minus - icon
Click on the Minus - icon to unfollow