I have imported a van which i modelled. But one of materials didnt apply and i want to edit from unreal , then assign a material there . Can i edit my object ?
You can change the material applied to the mesh (if there are slots). https://docs.unrealengine.com/en-US/Engine/Rendering/Materials/IntroductionToMaterials/index.html
If a material slot is missing you need to fix it in Blender and reimport.