For the record, those are not my trees ;-)
I’m just a designer hoe occasionally happens to try help out fellow designers.
So to recap, you should have get a folder with unique name (name of the assets) and it contains some sub folders named meshes, textures, materials and blueprints (all containing .uasset files), that complete folder and all its content you should place in the content folder of your UE4 project.
If you do not jet have a UE4 project then make one and give it a name and save it to a preferred location, close UE4 then go to the project folder UE4 just made. It has a bunch of sub folders and one of them is named “Content”, that's the folder you should place folders with assets in, so drop in your folder with the assets right there.
Now go back and reload your project, UE4 should now also load up the assets contained in that folder and all dependency’s correctly in place. The folder should now also be available in the UE4 content browser where you can enter its sub folder named “meshes” and just drag and drop assets you find there in the scene (all material and texture should be on it).
Note, “remove any filters in content browser if there are any applied”
This is all assuming the artist did a nice job organizing in this way, if not, then one can indeed get ready for bunch of manual assignments.