Here's how to do it.
Start by drawing your x axis and your y axis. It looks just like a big plus sign. The x axis is the horizontal line. The y axis is the vertical line. The point where the two lines cross is the origin.
Draw some short tick-marks on your axes.
Label your tick marks.
On the y axis:
the tick marks above the x axis count up from 0 starting at the origin.
the tick marks below the x axis count down from 0 starting at the origin.
On the x axis:
the tick marks to the right of the y axis count up from 0 starting at the origin.
the tick marks to the left of the y axis count down from 0 starting at the origin.
Now put your pencil on the origin. Move your pencil straight down 9 tick marks. Draw a dot here.
Now put your pencil on the dot you just made. Move the pencil up 3 tick marks, then move it left 1 tick mark. Now draw a dot at that point.
Next, connect your two dots with a straight line.
Next, give yourself a pat on the back because you have just graphed y=-3x-9 !!!!!!!! :) :) :) :)