Wiring of standard RS-485 devices is quite straight forward.
The interface is marked with a + and a -.
It may be described as TX, RX or A or B or various other descriptions depending on the manufacturer. In all cases, the + is always connected to a + and the - always to a -. This is normally in series, e.g. from DVR + to Controller + to Camera 1 +, to camera 2 +, and then the same process for the -.
If using particularly long runs, the final device in the run must be terminated. This is normally achieved with a termination switch on the device. Refer to the device manual.