The packages are bare bones assets. But you can find the specific documentation for the pack you are buying on our main support page. Both the UE4 and Unity5 documentations can be found there(if applicable).
Note: There may be some in engine specific tech art that does not transfer to the raw files. This may cause some files to have unknown set ups, something like a 2nd UV set. You can refer to the documentation page, or even install the free copies of UE4 + Unity 5 engines and open our packs from there since you now own them all!