This video will show you how you can add multiple materials on your models. I am going to be using 3Ds Max as my 3D modelling software, but you should be able to follow along and get an idea of how to do this with your modelling application of choice.
https://dev.epicgames.com/community/learning/tutorials/lE7e/unreal-engine-how-to-add-multiple-materials-on-your-model