Can't Change Icons in Dock

[jwoodsy]

Ok so I am new to mac and I would like to change my icons on my dock but for some reason only one pack I have downloaded so far has worked. All the other sets I've tried (3 or 4) come up with the preview icon when I try to copy them onto the default icons. Does any one know why this is happening and can somebody please tell me how to fix it? Thanks

 

[rprebel]

Does the preview say .ico or .icns? I don't think .ico files work in OS X. Could be wrong about that.

 

[GGJstudios]

Just a few of many threads on this topic, found by searching the forum with MRoogle:

Dock icon vs Finder Icon
How Do U Change Dock Icons?

 

[jwoodsy]

I know how to change the icons because one pack i downloaded works but when I try to use the others it shows up with the preview picture and says icns