If you already paid to download iPhoto on your iMac, you can re download the same app for free using the same Apple ID on your laptop.
How to re download apps from the Mac App Store:
Open the App Store. From the menu bar click Store > Sign In
Click Purchases from the top of the App Store window.
Select which apps you want to re download. Then right or control click where you see Installed then click Install.
If you have problems re downloading iPhoto to the laptop, uninstall the current copy of iPhoto (Iphoto8) first using this utility > Download AppCleaner for Mac - Uninstall your apps easily. MacUpdate.com
That will not only uninstall the app but all the associated files.
That does not delete your iPhoto library. That is stored in HD > Users > your account > Pictures > iPhoto Library.
Then try downloading iPhoto on the laptop.