If you want to add it I'd rinse it really well in a bucket, flushing it a couple times, then add fresh water to the bucket, stir it well, let it settle a bit, take a large jar of water out, and pick up a good handful of sand off the bottom and examine the jar of water and the handful of sand closely, then drop the handful of sand into the jar and watch it.
If you still want to add it, I'd fill the bucket of sand with freshly made tank water, and add an airstone. Let it sit for a week and monitor the PH, ammonia, nitrites and nitrates and whatever else you can. Examine the water and sand again and if everything still looks good and you still want to add it I'd say go for it.
I'd put the sand back in a ziplock bag with clean tank water while making sure the temperature was close to the tanks temperature, then flip the bag upside down, lower it over where I want to spread the sand, open it up and gently disperse it.