I had my molar crowned first, and did root canal from bottom of crown, because of infection, pain etc. after root canal, when do i know it went well?

No pain: The dentist can best tell you for your situation. However, the absence of pain is a nice sign.

About a week: A root canal from the bottom is typically done only after a conventional root canal treatment had been done. This procedure is called an apicoectomy. If this is your case, then your symptoms should resolve within a week. If a root canal was not done on that molar previously, you may want to see a specialist.

Root canal: If the tooth is not hurting and there is no swelling, the treatment was probably successful.