So basically you have rooted your phone and upgraded with a custom rom (CM10.1) and want to revert back to original firmware? As you only mentioned "successfully rooted" in your post.
Just put your device into download mode (hold vol down+homekey+power) upon booting.
Connect your phone to a pc with a cable and start Odin.
Follow the same steps as you did with flashing CWM but instead choose your stock firmware at the "PA" option (unzipped .m5d file) & don't forget to uncheck 'F reset time' before the process.
You can flash roms (CM->Updated CM) through CWM without the need of a pc, but i'm not sure it'll work when downgrading to original stock roms. So for now your best bet is through Odin.
Stock Firmwares can be found at: http://samsung-updates.com/device/?id=GT-I9195
Make sure you pick the correct region, check your device info (system) for your baseband version if needed.
Sent from my GT-I9195 using xda app-developers app