Depending on your variety of airlock, attach it.
1. Balloon- Attach to the neck and secure it with rubber bands.
2. Commercially Airlock -stick it into the rubber stopper and stick that into the neck of the container. Fill the big piece up to the line with vodka or any other type of alcohol and put the smaller piece on top. Put top on the whole assembly.
3. Attach PVC through rubber stopper. Attach hose to end of PVC.
If you are using tubing airlock, you will need to submerge the hose into a jar or glass once you've placed the container it the proper location.