fizixx
Hover over any part of the answer or question and a small purple flag appears to the upper right of the answer or question.
Click it, and if it's a serious violation, click the: "I think this answer violates the Terms of Service" 'button'. Otherwise choose the other one.
Leaving any comments are optional. Usually the violations are starkly obvious and need no real commentary.
Sandy
The same way you report an answer.
To the right of the question, there will be a little "flag" that turns red when you hover your cursor over it.
Click that and proceed.
Anonymous
The same way you report an answer. Click on the flag next to the question.
Libraryanna
They hide it. Float your mouse over the upper right corner of the question, just past the first line. A red flag should show up. Click on that.
brian 2010
It's the same way you report the answer. To do this, hover your mouse to the right of the question and click on the flag for the abuse report form to appear.