You notice a texture glitch whenever you put on a specific piece of CC? This means that the texture of either one piece or another uses a texture space that was not ment for the kind of it. In this example you see that I work on a jacket. But some parts of the UV map in Blender use the space of bottoms and shoes. You can find the template of the Sims 4 UV map layout HERE. After downloading the image, just drag it into the left side of Blender and you can use it to see where to put your UV map.

Select the parts you want to move with L, B or C and then move it to a new spot with G. If neccessary you can size it down with S (but keep in mind that a small texture means less details).

Whenever you make changes to the UV map, you probably have to change the texture too, because both have to match exactly. If you need to know where to put the texture, you can always export the UV map to help you find the right place. Before exporting, make sure to select everything though!

You can put the UV map over your texture in a photo editing software of your choice and then adjust the texture accordingly. Super easy!

Need a visual explanation? Here is the tutorial in a video: