Channels are changed through the set top box, which should have its own remote. The TV itself just has to have the input source selected (that is, what cable is connected). It's usually HDMI, though if there are multiple HDMI inputs on the TV select which one by number.
If the cable from the wall is connected directly to the TV (no cable box) then you will need to run a channel scan in order to select any cable channels. The TV manual will have instructions on how to do this or you can call Telus and have them help you. Let them earn their money.