.
For regular spam, just use the "Mark as SPAM" button, not both buttons.
Once you've done that, your job is most likely done, and BLF thanks you for doing that.
If enough people do the same, the post or thread will disappear.
If you really think something needs moderation, then you can PM the admin.
There is a link near the top left corner.
But for regular spam, just hitting the correct button should suffice.
Also, you could post in the problem thread and let others know that it has a spam post.
Then others that agree with you might mark it as spam and then the post/thread will disappear more quickly.