If you have an existing P&T service you could either update the phone through your Telus online account(Overview > Phone > Change Phone).
**Note: Make sure that you have a brand new SIM for your phone and if your phone is a non SIM Telus phone, have the MEID ready which you can find at the back of the phone when you remove the battery and the back cover(it's one of the stickers at the back of the phone).
If you don't have an existing Telus account, you could get a SIM through the website or directly at the store. Then activate the phone through the website as well and if you have any problems with the activation, feel free to call Client Care at 1-866-558-2273 for further assistance with the account activation.
In case you go for self serve, check on these links..
Find a Store: http://www.telus.com/forms/stores/en/find-a-store.jsp?cmp=mobility
SIM Cards: http://mobility.telus.com/en/AB/hspadevices/simcards.shtml
Account Activation for Prepaid: https://mobility.telus.com/activation/prepaid/PrepaidStart.action;jsessionid=gvBMSKDDv0KFLjNHB9x6TXL...