How do I install pro tools so it doesn’t need the hardware?

Pro Tools is what is called dedicated software. Meaning it will only work if certain hardware is present. Protools uses other sound devices to process sound, it has no internal script to do so. So in short, to answer your question, yes you did spend money on something you cannot use just yet. However, depending on the version you have, there is hardware available in various price ranges.
Now there are 3 versions of Protools, LE, M-Powered, and HD. Each version requires different hardware to work.
If you have installed the professional version, HD, then you have indeed bought software you cannot use. Protools HD requires very expensive audio cards and interfaces to work. So unless you want to pan out several thousands of dollars for hardware, you should return it.
If you have bought the entry level version, LE, then there is still some hope. Interfaces designed to work with LE are reasonably priced, but still in the expensive range for most users. The Mbox, the digi001, and the digi002 are some options. Depending on what you plan on doing with your Protools, one of these external devices might be a good investment anyway.
If you are fortunate enough to have bought the M-powered Protools, you will only have to buy a new sound card/device to get it to work. M-audio (Formerly Midiman) is a company owned by digidesign. Digidesign has put out a whole line of protools to work with the M-audio hardware. If you buy any of the following devices, your Protools will work. These devices start at 50 USD and go to several hundred.

Supported m-audio brand devices for M-powered Protools:
ProjectMix I/O
Black Box
Ozone
MobilePre USB
Fast Track USB
Transit
FireWire 1814
FireWire 410
FireWire Solo
FireWire Audiophile
Ozonic
Audiophile 2496
Audiophile 192
Delta 1010
Delta 1010LT
Delta 66
Delta 44

Good luck, I hope this was helpful.