From your other post, you built a 4" J-tube
RMH. This would be considered an advanced
project, and has to be done exactly right to work well (or at all). It would also have a small output at best, only suitable for warming one room. What is your layout like: room size, connecting spaces, total house, chimney height above floor level, your climate...?
Asking about connecting to a chimney sounds like you don't have any such connection yet. If that is the case, it's no wonder you had issues. A 4" system would probably be incapable of functioning without a good chimney to add draft. Do you have any mass around the exhaust yet? Can you measure the temperature of your exhaust directly after the
RMH barrel, and at the location of your chimney connection?
What is the length from the barrel to the chimney connection? A 4" system would have a short maximum run, and two 90s would further decrease the length it can handle.