Most hacker/cracker software is not authorized as you can imagine.. So first step is to get your phone jailbroken.
It depends what kind of phone you have, but here's a video for iPhones:
Nest step is to find the right software to hack into Instagram profiles. Usually, you're not trying to hack into Instagram at all... But rather access a more vulnerable system that will allow you access to their login details.
Here are some ideas:
- Third party apps
- Email servers
- Phishing scams
I'm answering this to show people worried about the security of their instagram account what they could be up against.
Just to be clear, I don't recommend that you ever hack into someone's account. The answer above explains why!