are you talking about the furnace or the hot water tank? if it's your furnace, there's a good chance your motor for fan blower is drying up and needing some greasing.
you can buy the lubricant at any home hardware store, ie Canadian tire, home depo, rona, etc. as for how to apply it, take off the front cover of the panel off. locate the motor, look around for a small nozzle like opening. it may be covered by a cap, in such case, you'll have to screw off the cap to find that nozzle opening. apply the lubricant and you're done.