Unscrew the knurled knob at the bottom of the grip and insert a CO2 cartridge. Don't have a gun in front of me and can't remember which way it goes, but the neck of the cartridge should face the piercing pin. Then screw the knob back on - just finger snug, not tight.
Depending upon which model(s) you have, you next either flip the lever (if it has one) on the bottom of the above knob or tap the bottom of the knob (if smooth contour) on a flat surface to pierce the CO2.
Bolt is opened for loading pellet by turning the knob at the rear of the receiver (I think its a quarter turn) and pulling it rearward. Load pellet and return bolt to locked position.
Cock by pushing the cocking knob(s) forward until it "clicks" (note, first click is low power, second click is high power). These are the knobs that protrude from both sides of the receiver.
Older models had adjustable power screw on front of the frame (tensioned the hammer spring) and adjustable trigger.
There is a good chance the seals are dried out and the gun(s) will leak CO2. Tim at Mac-1 is the CR Mk1 guru. Check out his LD conversion!
http://www.mac1airgun.com/