Exporting ONLY exports the group you have to include all meshes, materials and image textures yourself. Go to Object Maker and go to that group you wanted to export. Choose the mesh you wanted to upload and load it. Then go to the tab called Mesh and in the Mesh box it should say what the mesh is called. The Material box has the material the mesh uses.
Example: RandomTree.mesh
Example: RandomTreeMat
That is the name of your mesh. If it was downloaded it would be in the Feralheart folder in the my_objects folder. So you just need to find that file called RandomTree.mesh, the material and texture image.