Here is an easy way to make your own at home, half the price of the tincture you buy in the store.
First activate the THC in your bud/concentrate by heating it up. You need to decarboxylate it.
Best technique for making tincture as follows
For 1000mg Yield
Heat up 1 Gram of Co2 or BHO hash oil in a small double boiler like this to 220-240 degrees F for ~10 minutes. Use a Thermometer, do not allow it to overheat.
Mix decarboxylated hash oil with 28ml or .9oz of Food Grade Glycerin or Everclear, while slightly warm.
Use a small funnel to put the tincture in a bottle with a 1ml dropper, like this
1G=1000mg = 1000mg/29.57ml or 1 fl/oz.
1ml dropper = ~35mg dose.
It is easy as that, if you have any cooking skills this should be a piece of cake.