If you do need to trim them, it's ok to just use nail scissors or nail clippers.
But only take off a little bit off each one as a tortoise has a blood vessel running through the nail and you don't want to cause bleeding.
By taking just a bit off, the blood tends to withdraw deeper into the nail, so a few days later you can cut another little bit off.
Be careful.
... What ever you do DONT CUT THEM TOO SHORT! They need their nails for digging, climbing etc.
I think the best way is to let them walk on the patio. Torts nails are quite long anyway naturally. If you post a pic if the nails then we can see if they need to be cut etc