Hello, I'm Eleparts.
There are no assembly instructions available for TB-302.
You can fix the wire by connecting the wire to the middle hole and turning the screw.
A metal plate can be fixed between two plastic parts.
A piece of metal can fix the wires by soldering.
The link below is not TB-302, but I think you can refer to it.
https://www.hificlub.co.kr/web10/board/brd_eqdb_view_n10.asp?table=brd_10268&pid=10097&f_lid=100093&lid=100&level=0&ishtml=c&p_f_lid=100133&p_lid=100
thank you.