Your piece will either have:
No finish
Already oiled
Waxed
Varnished
The first two will take oil - the dark colo(u)r is often called patina by those in the trade - it means the dirt of ages. i.e. dirt sticks to the finish and gets rubbed into the grain. Fresh wood darkens with the application of oil - I prefer teak oil.
You can apply wood stain to bare wood but it tends to be permanent (it soaks in) and still needs dressing with wax, oil or varnish.
On a wax finish it's hard work to remove the wax to apply something else - wax is best on a wax finish and you can get darkened waxes.
On a varnished piece you're pretty much stuck with it - big effort to remove all the sprayed on varnish.
If you decide to varnish your piece apply three coats of gloss and finish with a top coat of matt rubbing down gently and dusting off between coats.
So use teak oil but only if there's no wax or varnish on the wood - several applications - perhaps 3 over the course of a couple of days - the mild and not unpleasant smell will soon fade. You can re-oil as often as you wish - the more oil you use (within reason) the more dirt will stick and the darker the piece will become.
Peccavi
October 2009