If you're talking about critters, after a while you will see signs of life. Worm trails, pods scurrying on the surface, etc. If you're talking about anaerobic bacteria, then you should see your nitrate drop (assuming other things like skimming and nutrient input haven't changed. aLSO, You may see bubbles form in the sand bed as nitrogen gas is released.
These things often take awhile. In fact it can take several months, and many folks say that your bed doesn't mature for up to 12 months. But on the other hand, while all live sand may be created equal, it doesn't end up equally good after transportation. Sometimes "live" sand is dead as a door nail by the time we get it. Then you need to try another source for some seed sand like your fellow reefers or oh so generous LFS.