Do you mean textures for things (clothing or skin) that you have bought (IE: A texture for V3 Morphing Fantasy Dress or a Character addon texture)? For those you apply them in the Pose room. You go to the library/poses folder and once you have found the texture you want, click the single check mark at the bottom of the library window. As for the tatoos, have you been doing the "INJ body/face" for the character addon you have purchased? The face doesn't usually change very much, but the body proportions usually does, so if the tatoo was meant to be placed on a specific figure type, it might look odd if applied to a different one (IE: small hips vs large; thicker waist vs smaller)

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi