You will need to contact your PO to get the access codes and other information needed for your particular case. It can take awhile to get this put in place for your case so try not to get frustrated if does not work in a short period of time. This will only apply to you if you are on State probation. I am not aware of any municipalities having this system in place.
Follow Mr. Kimbrell's advice, he's absolutely correct. Let me add 2 cents that you didn't ask. When paying online (or any other way) print out a receipt and keep it somewhere you can find it. I just finished a probation revocation case where my client insisted that he had paid on line but the state had no records of the payment and neither did he. I can't say whether he did or did not pay, but without any proof, the judge believed the state that he did not pay. Keep records of everything you turn in to you PO.