Yes, this is possible, using a 12.7mm optical drive hard drive adapter, but it must be IDE. iFixit no longer sells the part, and it may be hard to find on Amazon today.
However, any hard drive installed will be bottlenecked, which cannot be avoided. This is a limitation of the IDE bus being capped out at 100 (IDE) or 133MB/s (EIDE). Buy a cheap drive or live with this bottleneck, but it won’t hurt anything.
As far as a guide is concerned, I don't know which CPU you have so I can’t find one. You will need to find the guide on your own, unless you can provide the CPU speed for your machine.