Upgrade my iMac mid 2011 with CPU to GPU

People told me to get GPU on my iMac mid 2011 I need to download Cuda and upgrade to GPU.
I dit that and got a messages “Cuda ar installed on your system”

I open up Blender 2.75 and inside preference box look under AddOns-System but there was nothing abouth GPU
Maybe my iMac ar to old.

Thank you.

CUDA will not work on your machine. CUDA is works only with NVidia graphics cards, yours is from AMD
You’ll have to stick with using the cpu.

OK. Thanks Richard.
I need to by me a new iMac.