Ah, I see. I was confused by the term "pairing," because that usually refers to Bluetooth.
The ability to use your S5 as a mobile hotspot depends on your carrier and your plan. Some plans include free tethering up to a certain monthly amount (my T-Mobile unlimited data plan allows me to use my phone as a tether for up to 5 GB/month), but other carriers require you to pay an extra fee to use the hotspot function. What carrier do you have?
If your hotspot is active, then you should be able to set it up by naming it and setting up a password for it (highly recommended so that no one else can piggyback off your tether and use up your data), then toggle it on from the Quick Settings. Once it's on, then on your iPad, you can look for that hotspot and connect.