Yep. Switch on the xBox, either via the button on the front or pressing the centre button on the controller.
Once on, change TV source, probably to HDMI (on the TV remote control).
When on the xBox dashboard (similar to a PC desktop), use the controller stick to move left and right through all the options, iPlayer will be present there somewhere.
Sorry if that was sort of 'idiots guide' stuff but I don't know what level of experience you have with the xBox.
Happy viewing!