/3/ - 3DCG

Is this the thread you ask for assistance in? If not, which thread?
I fucked up.
I am days old into Blender, so I'm following tutorials, for 2.8 as that is what I have. I do exactly what is said in multiple tutorials, and it doesn't work for me.
I am trying to connect the bones to the mesh, but it's not working.
I suspect because I imported a .obj from a different file it might have something to do with it? The light blue lined head from my first attempt. I liked the head, but not the body. I also made the body segmented as I want to animate the body parts separately.
Is it being segmented the issue?
Is it the un-applied mirror modifier?
Please assist thank you for your consideration.