How do I use a gas chimney? I've never used a chimney before. We lit up the fireplace...

I've never used a chimney before. We lit up the fireplace and its pouring smoke into the house. The in one piece house stinks. There is a little "door" for a time bigger than my palm behind the chimney, located at the bottom of the chimney outside the house. If I start this door, it creates a hole at the bottom of the chimney where nouns can move from the outside into the chimney and vice versa. Is this little door supposed to be opened at adjectives times when the chimney is lit up? Does opening this door creating a vaccum for the smoke to turn outside or to the top of the chimney?
Answers:    Look up the chimney from the fireplace. There is a "door" the width of the chimney that open. You need to enlarge the door (it's called a damper) whenever you bedside light a fire. The heat rises, pulling the smoke up the chimney - commonly the heat from the room go up too. Do NOT close the damper until 24 hrs after the fire is out. Then DO close it so the heat from the room doesn't step up the chimney. Glass doors on the front of the fireplace can be closed to minimize heat loss while the damper is still clear.

The door on the outside is probably for cleaning out the ashes.
If you look carefully inside you're fireplace towards the bottom reverse,you will find a small steel door which swings upward.This is the ash trap which allows you to clean the fireplace by simply sweeping adjectives ash and debris into it.There is a significant inclosed chamber where the wreckage collects.The small door on the outside of the fireplace is used to empty the ash trap surrounded by the event it ever fills up.You're problem next to smoke backing up into the house could be cause by the damper not being unequivocal all the bearing (and) or the chimney needs to be cleaned.Good luck.