The IDE cable, a (usually) flat 40 (could be 80) conductor cable that plugs into a 40 pin connector on your motherboard, at one end, and to one or two devices (a hard drive and/or optical drive) at the other end, which also must have 40 pin connectors.
Along with the cable plugged in you must also have a power plug plugged in, it should be a 4 pin plug.
Then you must also be sure that you have the orientation correct where those cables plugged in. You should see a red strip running down one edge of the flat cable. The connectors on the motherboard and devices should have a "1" or "2" or a "Dot" identifying the side that the red stripe side should be near. Do not rely on just the physical keying of the flat cable connectors, I have seen some cables key opposite of what it should be.
Along with the correcting installing the cables you may also need to verify the jumper settings on the device(s).
The old way of jumpering was to have just one device jumpered as the "Master" and if you had a second device on the same cable that it would be jumpered as the "Slave" Doing it that way the Master and Slave can be at either of the two connectors. But there have been some conflict problems with some IDE devices. Most computers, still using IDE, are now jumpering for "Cable Select."
The one nice thing about Cable Select is that you never have to worry about rejumpering a device when you move it. You can not mix Master/Slave configuration and Cable Select on the same cable. I think if you have two separate IDE connectors on your motherboard that you can have one cable using Master/Slave and the other using Cable Select.
(Note: two IDE connectors on the motherboard are becoming less common since everybody is going to the smaller, newer and faster SATA connections.)
The thing to remember, about using Cable select, is that of the two device connectors you can have, the one at the end of the cable is the "Master" device, and you must have something plugged at that end.
As for the other connector, the one between the motherboard connector and the Master connector, is the Slave position.
Again, those are just the designations for the connectors, you do NOT jumper the device as Master or Slave when using Cable Select. It is the position on the cable that determines its priority (thus the name "Cable Select").
One last piece that might be hindering your use of IDE devices is that if your computers BIOS has any setting that must be selected to enable the IDE ports. I can't help there. But if you tell us what your computer model is, and the model number of the motherboard if possible, then perhaps someone here can research that for you.
Good luck. I hope that helps.
can someone tell me what to connect the ide cable to please as i have connected it but it is not working