I just upgraded to 11.10 from 11.04 on my laptop (I don't have Windows) by downloading from the Ubuntu website. The laptop battery is in bad condition, but I was using it with the 11.04 plugged to AC all the time, and everything was fine.

After installing 11.10, the laptop seems to not notice that it is connected to AC, so it shuts down a few minutes after starting. I read that I have to type pcie_aspm=force in the boot command, so I tried accessing it by pressing the "F6" key while booting, and then the other F keys, but nothing happened. I also found that I can write that instruction in the terminal window, but I don't know in which file or location. I would appreciate some help, but I am not a computer engineer, so please write the instructions in plain English.