Roughly chop pepper, onion and celery and set aside
Cook pasta according to package directions, perhaps a minute or two less
Brown the ground beef in a pan, drain off excess fat
Combine ground beef, pasta, vegetables, tomato sauce and tomato paste in a large pot or oven-safe dish. Either finish cooking on stovetop (partially covered) over a low flame or in the oven (covered) at ~300F. Since everything has already been cooked this is really just to blend all the stuff together.