That depends entirely on where you got it.
If Epic doesn’t own it (or didn’t put it up in their store), they can’t give you the legal right to use it in UE games. Only the ones that own it can do that. 
Also, I forgot to mention. Epic only gives you the right to use their free assets in UNREAL ENGINE games only. So, if you use them in a different engine, you can’t use Epic assets in them for free there.