Hi Jake,
With a 4 inch telescope, your ability to find new asteroids will be limited.
But you can help to confirm the orbits of asteroids that are already discovered. This is done by observing the already known asteroid when it is predicted to pass in front of a star as seen at your locality. Just like a solar eclipse, which can only be seen from a particular place on earth ...but the star is not our sun, and the asteroid takes the place of the moon.
Asteroid occultations are something that is easy to do, even with a 50 mm scope (not a misprint !!) and the results are sent by the local area collector of results to the Minor Planet Centre for updating the orbital elements of asteroids.
Your best bet to find out more would be to read Jacqui Milner's excellent document on the topic here:-
http://www.occultations.org.nz/videotime/manual.htm
Regards,
Tony Barry
WSAAG