I dont know how.
You gotta earn forum 'cred.
gotta wear that forum tabard when you post
9 Likes
www.likethis.com ?
Sadly I cannot either, you have to level up 
Going to note one thing about trust level 3, all it takes is one forum suspension & it’s gone. Some times it doesn’t kick in right away & you won’t be notified when it’s gone. No idea how long it takes to get it back.
You’re not really notified when you receive it.
I didn’t receive it when it was first introduced, despite being pretty active.
Forgot about it completely, then noticed I had a new place to visit called “The Lounge”
It’s kinda the notification you have it, when you see The Lounge unlocked in the forum list.
When I first saw that I thought they added an off topic forum to attempt to clean up GD until I clicked on it and realized what it actually was and what it meant.