I have the software version from chicken smoothie, Chibi Paint, to edit the skin line art. I have not been able to open the PNG line art for the unicorn, because i dont think it has the option to. In the Skin Coloring Tutorial, it said that any version starting from CS will do. But I dont think mine is working and i dont know what other free photoshop software i should use. 

If you need more info about my problem let me know, I really want to create my own skins. 

Photoshop isn't a free software. You can purchase stand-alone version of Photoshop CS6 or subscribe to the Creative Cloud version but there's only free trial for a month, no free versions. Photoshop CS is the first version that is using clipping masks which I mentioned in the tutorial. It can't be purchased right now but maybe some users have the old version that they do not want to update. And I'm really confused why are you mentioning Chickensmoothie here as they are not software developers, not a part of Adobe company and do not have any agreements with Adobe to provide free Photoshop to their users. They're just another browser game.

I didn't mention Chibi Paint in tutorial also. I suppose that it may lack some functionality though I never worked with it and can't tell for sure. I know that our users use GIMP to create the skins, you can try this tool too. It's completely free.

Sorry for the confusion. I saw Beast Keepers advertised on Chicken Smoothie, a virtual pet adoption website, and i am used to chicken smoothie being called CS for short. Im not too familiar with many Photoshop software names so i got the wrong idea. Ill try GIMP, and thank you for the quick response.

Oh, I understand it now, thanks for clarification. Good luck with the skins and welcome to BeastKeeper :)