What do I do? My jade tree has this white, cottony bits all over it.

Help!

Sounds like you jade could be infested with mealie bugs which look like little pieces of cotton and can be seen on stems, between joints and backs of leaves. These pest suck the juices of the plant and can eventually kill it.
Spray the entire plant with either soapy water,or, a Q-Tip dipped in rubbing alcohol dabbed on each one you see (be thorough) or two part alcohol to one parts water spray on every inch of the plant until it's dripping wet, including underneath each of the leaves.
Do this again two more times once a week or until gone then keep an eye out.
If you miss any,you will get another infestation. Keep it away from other plants.