In order to install OwnSpy on your iPhone you will need to jailbreak it in the first place.

You can follow this nice tutorial for Mac or Windows or make a search on Google to find how to do that.

When your iPhone is jailbroken you can use a new app called Cydia to install great apps like this.

Open Cydia and search for OwnSpy, select it and install it!

Once OwnSpy is installed a popup will appear with the code you need. Write it down and complete the registration process.

Please note that this popup will appear every 10 minutes if you do not complete the registration process.