Welcome aboard! The previous owner was referring to a burn off. You can do this by building a nice pile of lump charcoal(Royal Oak or Western are both inexpensive and decent) to just below the holes in your firebox. Light your lump in a few places. I use Royal oak Tumbleweeds, but a cotton ball soaked in alcohol will do the same thing. Make sure all your vents are wide open. When the majority of the coals are red and ashed over, place your grates in the grill and close the lid. I believe someone around here has a temp and time guideline for reference, but unfortunately I can't recall who. It very well might have been @John Setzler, and if so I'm sure he'll chime in. I try to shoot for about 500 to 550f and wait until the awful smelling(think residual burned on grease) smoke clears. 15 to 20 minutes later I start to shut down the grill. This is achieved by closing all your vents. After it's cooled down, rake your coals around and clean out your ashpan. If your a bit OCD like some on the site(myself included), you may remove your firebox and shop vac the whole thing out. After that, you should be good to get grilling. Good luck and have fun!