If you purchased the tincture check the label for dosage then put drops under your tongue or in a cup of tea or water. Then wait. In about 30 minutes it should take effect.
Tinctures or lozenges that are held in the mouth may provide effects in 10 minutes or so. Swallowing cannabis, whether in tincture or other form, means it must go on a journey through the system that can delay the onset of effects for a variable amount of time, occasionally up to an hour depending on many factors like what else is in your stomach when the cannabis is swallowed. Alcohol based tinctures may be too astringent to hold in the mouth for very long, but glycerine based tinctures are also available. Whatever preparation is being used, begin with small amounts the first time and wait an hour to determine effects.