"There are two ways (to engange the nose when smoking )and they can be done independently or in combination of echother (if in combination, that is the major trick). The first method is using the nose as per normal, when you exhale the smoke from the mouth, do it in small and brief exhales only allowing a little smoke exiting the mouth. Draw back some of the smoke into the nose.. sort of, sniff the smoke you just exhaled. (I also recommend to "wave" the burning tip of the cigar in front of your nose and smell it in between you actually smoking it.)
The second method here is to "roll the smoke back" into your throat area and exhale it through your nose. I am not advocating inhaling the smoke at all!!! But imagine that you "lock" the air-pipe down to your lounges with your tongue and sort of "swallowed the smoke" almost like you do on a plane when you want to pop your ears. Then slowly exhale through your nose. This will allow the smoke to pass through the passage that links up the back of your mouth with your nose. My recommendation there is to do this with small amounts of smoke!! If your not used to it, or if you use too much smoke initially, it can create a burning sensation that is not pleasant. "