speaker wiring

i have a an am/fm cassette i am trying to hook up without a diagram. out of the unit i have four wires. red-power, black ground,two speaker wires-blue left +, andgreen right negative. to try out the unit i hooked the red to apositive battery terminal and the black to the negative which powered up the unit.how do i wire the speakers.i am using a two speaker system with two wire terminals on each speaker. the speakers work if i hook ablue wire and a green wire to each speaker but the balance won't adjust. i know i'm an idiot . what am i doing wrong ?1234

What kind of head unit is this? You should have more wires. You need a + and - for each speaker.'85 Toy

Well i've seen some old HU's that only have 4 wires for speakers 2 pos and 2 neg. never seen one with only one set. maybe your supposed to hook all the speakers to the one set of wires? In that case no balance and no fade.