To use substitution, you want to substitute something for another variable. So lets take the first equation and solve for y
2x - y = -1
2x = y - 1
2x + 1 = y
Now we can substitute 2x + 1 for y in the other equation
3x + 2x + 1 = 6
5x = 5
x = 1
now that we have x, we can get y
2(1) - y = -1
2 - y = -1
2 = y - 1
3 = y
So x = 1 and y = 3
