The installer places a new RealCADD Lib folder and a new Scripts folder in Documents >> RealCADD – prior to 4.60 these were in the RealCADD folder in Applications.
Drag your existing "RealCADD Lib" folder and/or "Scripts" folder from their current location (usually the RealCADD folder in Applications) to the RealCADD folder in Documents, so that they replace the new ones.
Depending on your system setup you may be asked to authenticate the move by entering your Administrator name and password. Also, depending on your system setup, simply dragging may create an Alias rather than a Copy. Holding down the ⌥ (Option) key while dragging will force a Copy.
The download will create a new RealCADD folder (in Downloads), which will contain a new RealCADD Lib folder and a new Scripts folder. Before you drag the new RealCADD folder to Applications, rename your existing RealCADD folder (say, "RealCADD_previous_version"). Now drag the new RealCADD folder to Applications.
Open your existing "RealCADD–previous_version" folder and drag "RealCADD Lib" folder and/or "Scripts" folder into the new RealCADD folder so that they replace the new ones.