Folder Icons

I am a new Mac user and don't understand why i can't change the folder icon/image on my Mac.

I have followed the instructions given. Copy/paste or drag the image to the 'Info' section of the folder. However after doing so, the image isn't displayed or previewed. Instead, only the words jpeg or png appears.

Can someone help me out here?

Thanks

New Mac user... new Mac?
If not, how old, what OS version... iMac? Mini? MacBook? etc.

I'm a new mac user and i have a MacBook Air.

I since sorted the problem and discovered that if the image name has a _ in it (for example Image_01) then it doesn't display. When I removed the symbol the image displayed fine.

I think it will take some time to get used to.
I would like to know the shortcut for editing something in the equivalent way we use F2 in Windows??

Thanks