If you have a tab you have to pay that off first.
If you need to put the new phone on tab you can only use a tab S (Tab M& L are available in store only).
The new phone will comes with a Koodo sim card.
On self serve > Mobile Phones>Swap Mobile Phones to enter your new sim card. Everything should be up and running in about 15 mins. You may have to restart your phone.
On a side note, I hope you reported you phone stolen so the thief cant use your Koodo mins/data and so it can be put on the national blacklist so no one else can use it.