If I have my own nexus 4 (unlocked) how can I get the ten percent off while purchasing a monthly plan online?

At point of activation it is added. If you are an existing customer you might like to call *611 to reach customer service. The best option will be to activate at any koodo shop or any other retail like best buy, future shop,... I don't think that ordering a sim card and a plan online will let you add the no tab discount. It should be automatically although since you are not purchasing a phone. In the worst case scenario you can call customer service