select the level you are working on and in modes menu select the landscape and your view port in unreal engine should look like this. creating a new landscape In the modes panel you can select the landscape mode and then change the setting to the following and then select create. (15 x 15 quads is well big enough for your first level.)
UE4: Step-by-Step to Your First Landscape Material Instance (Day 3/3: 3-Day Tutorial Series)
How to create your own LANDSCAPE MATERIAL in Unreal Engine
Frequently Asked Questions
How to create a landscape material in UE4?
Every landscape material should have Normal Maps along with Albedo/Diffuse textures. Insert Normal Maps that match the Albedo textures into the Material Editor. Again, you can Left Click and Drag the Normal Maps from Content Browser into the Material Editor the same way as you did with Albedo textures.