If you don't have off camera flash you need to get your on camera flash to direct the light from an off camera angle.
Turn the flash head so it points AWAY to the side of the subject. Bounce the light off a reflector held to the side, where you want the light to actually come from. Zoom the flash head manually to tighten it up, the bounce will naturally widen it and soften it quite alot. This will give you more flash "power" - you actually have the same power you started with, but you can use a smaller aperture.
To prevent the camera from burning out the background, look through the finder, notice the settings the camera gives you in aperture priority. Now start with that in manual settings (just copy them - say 1/15 @ f8) shoot and see what you get on the screen. If the background is black you are close. If the smoke is not bright enough it is the flash you need to alter - bring the reflector closer to the smoke and fire the same setting again - it should brighten the smoke a little.
Just work round a starting aperture and shutter speed that is sensible (above is a goodish starting point). Then either drag the shutter a little longer (go down half a stop to 1/10, or even 1/8 and see what happens.) If the flash is a bit weak -open up to f5.6
You will get better results by having the room dark - use a little red torch to work by so you don't trip over naything. Get everything set with light to see by, then turn off the lights to actually shoot. You could set the timer and then walk to the light switch counting and flick the room light off a second before the camera/flash fires. Then turn it on and go back to the camera.
You'll work it out how it suits you set up.