First find your slope. Staring at the point at (-6,3), you’d go “down 5, right 6” to get to the point at (0,-2). That’s your slope: -5/6
Next find your b-value, your y-intercept: (0,-2). For the slope-intercept form, you only need the -2 as your b-value.
Putting that together into slope-intercept form, y=mx+b, you’d have an equation of y = -5/6 x - 2.