You can graph that by looking at the y-intercept first. That's where you start to put a point in the coordinate plane or graph.
So go down 1 below 0.
Next, look at the slope.
We know that y = -2x - 1 is in slope intercept form (y = mx+b)
So -2 is our slope. It will be -2/1 because we need a fraction to graph the rise over run and all whole numbers can be a fraction by making 1 as their denominator.
Look at the attachment.
Starting from -1 (y-intercept), go down 2 (-2) then right 1 (1).
To complete the line above, keep the same value and reverse their sign/symbol. So -2/1 will be 2/-1. It goes up 2 then left 1.
I hope you understand and find this answer the most helpful! :)