If two forces "balance" each other, that means that they add up to zero.
THAT means that they must have exactly equal magnitudes and exactly opposite directions.
If you want to draw a picture of a pair of two balanced force vectors . . . .
1). Draw two arrows with exactly the same length.
2). Flip one of them over, so that it points in exactly the opposite direction compared to the first one.
3). Place them tail-to-tail.