For starters, forget positive or negative. Just do the multiplication. When the mathematical operation is completed, you determine whether the answer is positive or negative by looking at the signs.
If multiplying POSITIVE by POSITIVE the answer is POSITIVE
If multiplying NEGATIVE by NEGATIVE the answer is POSITIVE
If multiplying POSITIVE by NEGATIVE or NEGATIVE by POSITIVE, the answer is NEGATIVE
As example: 1 x 1 = 1
-1 x -1 = 1
1 x -1 = -1
-1 x 1 = -1