Well, of course I don’t mind, dear. Not after such a nice compliment! :) JK, I’m always happy to help. ;)
It’s pretty easy, actually. All you need is a paper texture (there’s plenty on dA). You’ll need to put it on top of your (already coloured and sharpened) picture and set it to “multiply”. Play around with opacity for a bit.
Here how it looks before applying the texture:And after:
Hope, that’s what you needed. If not, feel free to contact me again! :)
Best of luck!