How do I set permissions on an object?
Permissions let you control what other people can do with the things you create. The current permissions involve Copy (whether someone can make copies of your work), Modify (whether someone can change your work), and Transfer (also known as "Resell/Give Away"). If the the object is inworld (rezzed), right-click it and choose Edit, then navigate to the General tab. If the object is in your inventory, right-click it and choose Properties. The entries you want to change are listed under Next owner can:
Modify: Checking this lets the next owner modify your creation. Unchecking it denies any modifications.
Copy: Checking this lets the next owner copy your creation. If they drag the object from inventory to inworld, they will retain a copy in inventory. Unchecking it denies any copies; if they drag the object inworld it will leave their inventory until taken back into inventory.
Resell/Give Away: Checking this lets the next owner give your creation to someone else. If the object permits Copy, they can sell copies. If the object does not permit Copy, they can only sell the original. Unchecking this means the next owner cannot give the object to anyone else. If the object permits Copy but not Resell/Give Away, they can make as many copies as they want for their own uses, but can never give a copy away or sell it.