You will need to reinstall it.
If you purchased it as a retail box version, with a family license, reinstall it from the original installation disk.
If if was purchased as a free-standing application via the Mac app store, you might find it in your Purchases list, and be able to download and install it again.
Copying the application package from your iMac will probably not work, although using Migration Asistant to move only that application may be a possibility.
Beyond those steps, you might try contacting Apple Support to explain the situation and ask what can be done.
Regards,
Barry