how to unsubscribe threads?

As title says, I can subscribe any thread, and having the subscription.php page bookmarked I can quickly see if there are new posts in discussion that i’m interested in.
But now, if i change my mind on some thread and no longer want to follow the discussion, how can I unsubscribe? did I miss some command?

Settings / Subscriptions.
Select threads you want to unsubscribe to and at bottom of page use Selected Threads / Delete Subscription

Wow, it took a little to find it even with your explanation: that button doesn’t look like a button!
thanks a lot!