if its not in one piece then its broken.
There are different kinds of jacks. If it is a scissors jack, insert the loop of the handle into the hole, as to turn.
The car jack will depend on make and model, but here is the basics
Your car jack should have 2 to 4 pieces. There should be the main body + (maybe a removable top) + a base plate + the stick.
Normally its a single unit with a stick.
If this is the one that came with the car, there is special holes under the car for it to fit in. Look in the owners manual for this information or google it. It will have a full instruction guide on this