Since your device is rooted, we will use the good old custom recovery method. As a reminder, here is the procedure:

1. Download both zip files given above on your android device.

2. Place both files in the root directory of your android device.

3. Turn off the android device and restart in Recovery Mode (for samsung-> Home + Power + Volume Up until the logo appears or the third vibration and release & for other android devices-> use google to find how to open recovery mod or clockworkmod for any android device).

4. Perform a factory reset by selecting and confirming the option "Wipe Data/Factory Reset" then "Wipe Cache". Some users prefer to ''Format System'' / ''Wipe Dalvik Cache'' at this point too.

5. Then select "install zip from sd card" and locate the CM 11 zip you downloaded before.

6. Click "Yes" to confirm.

7. Next, flash the gapps zip file.

8. Return to the main Recovery Menu and select "Reboot System Now".

The first reboot on CM 11 may take a few minutes. Let us know how you like it!