For re-useable items, you can save them as symbols. open the library palette, at the top, navigate to the 'My Symbols' folder, it may or may not be empty, its located in windows documents - Turbocad (whatever version) - Symbols. This is the default of where TC expects to see your own Symbols. Simply drag your instruments / drawings into the Library palette and TC will prompt for a name. after that, if it doesn't present the 'My Symbols folder to save in - navigate to it and save. Then repeat for the next instrument.
See this help file
for details of the library palette.