Today Crosman air gun company owns the rights to the Hahn BB line of air guns. The rifle was made between 1958 to 1971. See the link below for a detail drawing of the parts.
How do you put WHAT. A pellets in the rifle, a BB in the rifle, Put it back together. your question is incomplete.
Gun shop or gunsmith
Into the clip or magazine on the underside of the rifle, in front of the trigger
WATER
Go to www.crosman.com and click on "Download a manual" you will find you rifle there. It will give you an exploded view of the rifle.
You get an explosion.
See the link below for the parts diagram.
Put the Rifle Down was created in 2003.
put organic soap and bleach together the put a suchen cup under the lid then put a hole in the lid then put paperclip pin then you got a musterd gas gernade.
Take a bite of humble pie and ask a gunsmith for help.
The JC Higgins Model 21 is a pump shotgun, not a rifle. Reassembly should be done by a competent gunsmith.
Put the ammuniton into the magazine and put the magazine into the rifle, cock it and pull the trigger..