PhotoShop Modding?

I just got photoshop and was going to try my first texture mod but when I selected the DTX file It said it was not the correct document? What do I need to do to make it work?

http://www.mpgh.net/forum/293-combat...-make-mod.html
watch this.
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u( need maybe DEDIT)
convert the .dtx with dtxconverter to lichtech
(then put the file in the dedit map: textures
open dedit )
go to textures right clck on the mod and export .tga file
then u can open it
lmao writed this all for u
Thank me...! pl0x

My first attempt at a Login Mod ended with lots of Grey and Yellow 15's and a language I dont understand. I don't know what I did wrong. Any suggestions?