edit button!?

where is the goddamned edit button?
I really need one, especially for the last post, but for sure in future..
It seems that my teacher wanted me to present in the next lesson. So I got more time to prepare, but there will be also higher expectations.
Two of my classmates were out of their senses in the first lesson and we wondered what they took... I try to think if something happened, but my everyday live is too boring to mention soemthing.