To read codes you simply connect a wire to terminal 1 on the diagnostic socket, and earth. Switch ignition on and your MIL will then flash any stored trouble codes.
Each code consists of two groups of one or more flashes. The long flashes are 10 units each, the short single units.There is a short pause between flashes and a long pause between codes. Ie two long flashes followed by four short is trouble code 24.
To erase trouble codes from memory disconnect battery earth lead, wait 15 seconds and then re-connect :)