Deleting information on iPhone 5s when stolen?

My iPhone 5s has recently been stolen, and I'm concerned that the person who stole it will be able to look through all of my information, including my photos, instagram, and various other types of apps and notes I have left on there. Is there any way that I might be able to delete the information on my phone through my computer? However I have not set up the Find My iPhone app. Or at least how can I log out of instagram on my phone through my computer?

I'm afraid if your phone had no passcode and if Find my iPhone was not set to on directly from your phone it is impossible to do anything. If you had a passcode, the thief will most likely figure out how to restore to factory defaults and use it as a new phone. If you didn't have a passcode, then you're pretty boned.

Though on.

First thing first, make sure to report your phone lost/stolen through your carrier so they can flag it down.
DO NOT REPORT IT TO APPLE! THEY CAN'T DO ANYTHING. So save yourself and that poor advisor a headache.

if your believe that your apple id information maybe at risk make sure to change your passwords and contact your debit/credit card company to request they change it.

The last thing you can try doing (which may not help, but is worth a try) is to go on icloud.com
sign into apple id/icloud account and set it up there. It's possible that if some one finds your phone as soon as it connects to the Internet the phone will go to lost mode and once in lost mode you can track it and in worst case remotely restore it.

And change your password to instagram as well.

Best of luck!