you dont need to find out on which side of the cable you should use... as long as the jumper settings are correct...
one more thing if you could notice one part is longer and the other is shorter.. the longer part should be placed in the mobo and the ahorter part and middle part should be placed in the hdd or cd... this is beacause the distance from the mobo to either the cd or hardrive would use the longer part of the ide cable