You want to start by isolating y on the left. In your equation you can subtract 3x from both sides to achieve it.
y = -3x - 2
The resulting equation is in slope-intercept form y = mx + b so in this case we have m = -3 and b = -2
Now the y-intercept point is always (0,b), which in this case is (0,-2).
For the other point, use:
slope = rise / run
In this case this is -3 so you can go right 1 and down 3 and wind up with (1,-5) as another point.
Now draw a straight line through the two points.