By Hector
The 8 pin header is a pin header ( On Arduino its generally a female pin header where you can insert male pins). Where did you find this information? It is not enough information to give you a good answer. Usually the place you select 5v or 3.3V is marked.

I hope this helps. If you have any more questions please let us know.
By zhalim
Thanks for the info. So the 8 pin headers are extra 5v/3.3v and GND. Tried looking for any jumper to select 5v/3.3v but found none on the board but there is a marking on one side 5v and the other side 3.3v. maybe the board supply both voltages simultaneously but on opposite side.
By Hector
Hi Zhalim,

The 8 pin header has 8 female pins on it. The 6 pin header has six pins and contains the 5V and 3.3V pins. You don't need to set a jumper, just use whichever voltage you need for your project. It provides both voltages.