I am going to assume this is an entire new phone and you are new to Koodo.
You will need to bring the phone you have to Koodo, provided it is unlocked or locked to the Koodo network, you will be able to purchase a SIM card for the phone as well as select a plan and make your new account. This can be done at a Koodo mall stall.
That's all you need to get the phone activated and on the network. After that, you will want to create a self-serve account over at www.koodo.com/self-serve
Note that you cannot use self-serve until you register your phone with Koodo and get it activated.