We usually wrriten equation for a line this way,
y = mx+c or y = mx+b
m = slope and (c or b) = y intercept
First you have to find c (y intercept). To find c, replace the coordinates of the point and slope value to the equation.
-1 = -2/3 * 3 + c
so c or b = 1
So equation for the line is
y = -2x/3 + 1