Adding thermal copper pour to pads

Hi,

I am a beginner with PCB editor. I am trying to add copper pours over some LEDs for better thermal dissipation, I appreciate it for any suggestions on guidance on how to do that. My idea is to create copper pours/thermal pads to help with thermal dissipations as indicated by the picture below:

If I try to pour copper on top of the LEDs, it will crop the shape out so I cannot cover the LED with it and thus won't help me thermally. So, now I am trying to do it though modifying it with pad stack editor. I really do not understand how to do it, whenever I try to create something either I don't see any changes or the whole pad that I am trying to edit disappears ( or all of them If I choose all instances). How can I achieve what I am trying to do? Please keep in mind I am a beginner and would like as much info. as possible. Do I need to create a flash symbol? what's the significance of the anti-pad and why do I need it and what do I need to put for the offsets to achieve this for the thermal and anti-pads, or if I am missing something or if there's a better way please let me know. Thanks a lot! 

Best regards.

Neil Mustafa.