Step 1: Right-click the name of any protected (but currently unlocked) notebook section whose password you want to change, and then choose Password Protection > Change Password. (If this option isn’t available, it means that the current section doesn’t have a password.)
Step 2: In the Change Password window, type the current section password into the Old Password box.
Step 3: In the Enter New Password box, type the new password that will replace the current one.
Step 4: Type the new password again into the Confirm Password box, and then press Enter.