should my speakers plug into an outlet or back of my computer?

Answer 1

both most likely, depending on how good your speakers are, they definetly need to plug into the computer the power is for speakers that need more power then the comp can give. I. E. nicer speakers

Answer 2

There are cheap speakers that just plug in the back of your computer via a 3.5mm mini-jack connector (usually green).

Then, there are the good type that plug in the back of your computer with a 3.5mm mini-jack and a power outlet. By applying power to a speaker set, you get a louder and robust sound.