Mask is doing something wrong

[sykesccorp]

this is the most noob question that i know that i have ever posted here…... :grin:
i am making a doom orpg and i got textures and i painted the back ground black and re sized them so now they are all fine but when editing when i got to make a mask the texture has got black behind it (well no duh you might be thinking but what is the see threw colour) Ive tried and tried but it wont work Ive got this screen shot to show you what i mean if you don't understand