light textures

Ok, this may be the stupidest question ever but I do not know how to upload light textures on my PS7. Do we upload it in the PS or what? I tried to open a light texture (manually from My Documents) but they won't blend nicely like a brush or a gradient when they're used on a picture. So, I'm wondering, do we upload it in our PS or open it as a file when I want to use it? If it's the former, can you tell me how?? Please!! I know this question is kinda 'DUH'. Sorry.