I have normal computer speakers for my computer but I would like to add my other sound systhem to it. My other system only has the the black and red wires but I know I can put it on my computer because my friend did it.

If opened up my normal speakers and I realized that they had red and black wires aswell. I would like to know how to put my other speakers on my computer because the current speakers I have aren't very loud and good.

you just have to solder the right jack to the end of your speakers wires. However, the speakers must be powered or have adequate amplification to work from the computer's sound card.

My advice: invest in some higher quality speakers made for computers.