It's really difficult to see what's going on there. But my guess is that the model was exported as separate meshes, each with their own material.
For best performance, you want to combine the mesh first in Blender (or whatever) if it's supposed to use the same texture, and then map out the UVs correctly.
If there is some reason they need to be separate (like for animation) then you have to click on the mesh instance on the top right, then click on each mesh inside and assign the same material.