You can use the scentFX jars by just opening the jar and placing it on a table for the duration of your game, movie, etc. The jars are designed to spread the scent slowly over a small area to create a subtle atmosphere. Because they don't emit smoke or spritz oils all over the place, the scent fades fairly quickly once you close it up and put it away. If the scent persists, an open window or a fan should be enough to clear the air.
You can increase the strength of the scentFX jars by shaking the orbs in the jar, pouring them out onto a paper plate, placing them in a warm location (e.g. a sunny window - do not use a candle tart melter), and/or arranging them so air flows past them (e.g. in front of a fan).
Please note that, due to their size, the scentFX jars will create a more intense scent in a larger area for a longer period of time than the orbs in the sample packs.