How do you bleed the air from the system?

How do you bleed the air from the system?
It depends what system you're talking about but assuming it's the brake system.
Top up brake fluid reservoir. Have an assistant pump the brakes several times ( 5-10 ), then hold pedal in until you say when. While assistant is holding, go to furthest brake from reservoir and open bleed screw until fluid and hopefully air escapes. At this time assistant will note that pedal goes to the floor. Close bleed screw. The assistant can now release the pedal. Repeat the procedure until no more air comes out at that brake. Then move to each brake from furthest from reservoir to closest and repeat the same procedure until all are done. Check fluid in reservoir repeatedly during the process and when done.