Why are you not using the landscape? - is it a personal choiche or do you just not know what you are doing? (It could go either way, if you really know what you are doing you probably wouldn’t use the landscape since it comes with really bad performance on mid range machines).
Regardless, the process is much the same.
Create a material, put the texture in the material,
press u and click for the uv / coordinate
Drag the pin out and multiply.
press S and click for a scalar parameter, name it tiling.
connect to the multiply.
Put the output of the multiply into the UVs, plug the texture (3 color) into the Albedo (base color).
Then create a material instance (right click material, choose correct option).
And apply the instance to the mesh, or landscape.
open up the instance, check the tiling parameter, play with its value.
Last but not least. Create a new empty level.
pop in a directional light, and a skylight.
pop in the BP_skysphere
save the level.
Click the sky, set up the direction light in the properties panel. It will auto update to the correct time based on the light rotation.
Proceed with landscape creation or adding of a mesh/with material.
Once that works you can and should add a post proces, unbind it, and set it up as you want/need for your project.
As a general note, forget completely about importing stuff.
Import the base things yourself and create the parts (materials, etc.) in engine.
relying on a 3d app to set up your materials is bad practice and 99% of the times completely useless, since more often then not projects will use some simple master materials and customized instances.