First thing is to inform you call forwarding is not free. You need to make sure you have the call forwarding add-on or else you will be charged per minute for that call forwarded (yes it will be for the entire length of the call).
As for activating the call forwarding, there is no way to complete this online, it must be via your phone.
I also believe that since you are roaming, if you forward a call while on a roaming network, you will be charged roaming for that forwarded call. Let me flag a rep to confirm this.
https://www.koodomobile.com/en/help/call-forwarding?srsltid=AfmBOopUkD8NZOFWNePKwXch1rhtpUSNczHj5aos-vQcsX3N4xEkY2Np
Hi there @tcrecampbell
Unfortunately, Call Forward cannot be set through the Self Serve account. You can only add the feature through your online account and set it up on the phone by dialing the activation code + the number you want to forward to.