The key to being able to solve problems like this is knowing what exactly to do with the given information.
Like it says, start at (1,-4) and then use the slope of -3 to keep going down. One other thing you need to keep in mind is that the slope always goes from left to right. Even when the slope is negative, you go over to the right, unless you're working your way back up.
For the slope of -3 you go down 3 but over 1 to the right: -3/1. If you wanted to work up with a negative slope, you can go 1 over to the left and up 3: 3/-1. Either way the slope will be -3.