will currently be set to configure the drive as a 'master', and as you say, that must be changed to set the drive as a slave. It's normally an easy procedure - the jumper positions are marked, but of course you need to know what the markings mean.
Take a look at the back of the drive, and locate the small jumper block - it will probably have a series of numbers (many Fujitsu drives do) above and below the little jumper pins.
At the moment, you should see that the small plastic jumper is on pin numbers 7 & 8, which correspond to the master setting. Remove the jumper and place it on pin numbers 3 & 4.
Now the drive is configures as a slave, and you can connect it to the spare connector that's on the ribbon cable running to your existing hard drive. Make sure that the cable connector is properly seated, and that you connect it the right way around - the faint red line on one side of the cable corresponds to pin number one on the drive connector. Hold the drive with the top upwards and the rear facing you - in this postition pin 1 will be on the right. The cable connector can only be inserted in one way, and you can tell what that is by carefully studying the pins on the drive and the cable connector.
Once that's done, slide the drive into the drive bay, underneath your existing drive, and secure it with the appropriate screws. Don't forget to connect a power lead - use any of the spare connectors which you'll see inside the computer case.
Close the case, and power up the machine - you should find that the spare drive is recognised and that Windows assigns a drive letter. Once that's done you can right click on the drive icon in 'My computer' and select the 'format' option.