If you are simply going to add it in to an existing computer make sure it is either added as a slave drive (usually change the jumpers on the back)and plugged in to the same ide cable as your current hard drive
plug it in with an ide cable of it's own to the secondary ide controller on your motherboard (usually next to and identical to where the ide cable from your original hard drive is plugged in)
Once it is in, switch on your computer and wait for windows to recognise it, if it isn't there check the cables or maybe you need to change a few bios settings.
When windows "sees" it simply right click on the drive icon and choose "format" option. This will wipe the disk clean and allow you to use it as free space