Many owners use a supplement like Mazuri which is rich in fibre and has a good calcium/phosphorous/d3 balance.
If your tortoises diet is mixed and good it should not strictly be necessary, but many torts love it.
Some don't.
For my Russians, I sprinkle a little of the TNT supplement on their leaves about once a week. The way I do it is to take a salt or pepper shaker, add a mix of TNT and calcium to the empty and clean shaker, then just a light sprinkle one a week. Just enough so that you can barely see it on the leaves.