You should start with the bleeder furthest from the master cylinder.
Do one bleeder at a time working towards the master cylinder.
Usually left rear, right rear, left front, right front,
Get the right size hose (clear is best, but black works (you can see the air bubbles in the clear hose.))
Get a small jar with a cap on it and punch two holes in the top.
Put the hose through one of the hoses.
Put enough brake fluid in the jar to cover the bottom.
Push the hose down into the fluid in the bottom of the jar.
With the jar still connected set it on the ground under the bleeder screw you are working on.
At this point you can proceed with either the gravity method (one bleeder at a time), or the pump and hold method.
I use the pump method.
Now very important. Do not let the master cylinder go dry! At all times there should be at least a 1/2 inch of fluid in the master. Let it go dry in the process and you have to start over.
Pump and hold method, you need two people. The pump and hold method, the brake pedal is pressed while one bleed screw at a time is opened, allowing air to escape. The bleed screw must be closed before releasing the pedal, or a one-way valve must be fitted.
Place the end of you hose below the level of the brake fluid in the jar. You will see the air bubbles raise to the surface of the fluid in the jar. Most of the "draw back" into the tube will be fluid as the end of the hose is below the level of the brake fluid in the jar.
This is very frustrating work and chevelles are tough to bleed for some reason.
Here is a pretty good You Tube on Pump and Hold. They are demonstrating on the left front (incorrect, start on the left rear).
How to Bleed Disc Brakes - YouTube