The wiring of the INA 125P is quite complicated. I mounted the amplifier on small section of proto-typing board with terminal blocks for the connections to the Arduino and load cell. This gives me a bit of flexibility and means that I could easily use the amplifier on other projects. The wiring is shown in the photos and schematically on the figure below.
The gain of the amplifier is governed by the resistor. Increasing the amount of resistance will reduce the gain. You may need to play around with the gain depending on the range of readings you want. For example my load cell is rated for 5 kg and placing only 1 kg on the load cell gave a reading of about 860 on the A1 analogue pin of my Arduino with 10 ohm resistor. When I increased the resistor on the INA125P to 100 ohms the reading reduced to 140 and was 440 for 3.5 kg. This gave me a good range of values over which to map the output.