If it is smoking, that means that whoever had it before you didn't complete the seasoning process, and the remaining volatiles from the previous application are now cooking off.

Before you cook with any of that iron, I would at least put it all through one seasoning session. It will ensure that the pot is ready to cook in and is sterile.

Typically you will want to put a thin coating of oil or grease on the inside and outside of the pot/pan, put it in the oven at 450 to 500 degrees and let it burn in for about an hour or so. It will smoke, and if you have a bbq grill that will hold the pot I suggest doing this outside instead. When it is done, let it cool in the oven/grill, and it should come out shiny black and the surface should feel bumpy but smooth and not tacky or gummy.

The seasoning isn't burning off, it is getting set proper, and you can expect that to happen everytime you season the pot.