How to install new chandelier when impossible to fish wires?
Assuming you have wires from where the green line starts, this should be simple enough, provided you're OK with some wires showing.

You'll want to buy 


A heavy-duty (fan rated) metal fixture box (octagon) and screws to mount it into the top beam. I would suggest you buy a box with clamps built in
If you didn't buy the box with clamps, buy a NM clamp that fits the knockouts
Finally, buy the proper size wire in armored cable, as well as clamps to secure the wire to the beam


If you're wanting to add a switch, buy a surface mount metal box, switch, and switch cover