Do you mean HDMI Input? For example, your cable box is connected to the HDMI-1 port of your TV...and your Blu-ray to HDMI-2. After switching to your Blu-ray, you can't switch back to your cable box without rebooting?
I don't know what box or remote you have, but the remote should have a TV Input button. Mine is on the lowest right-side. You press the button to navigate Inputs and keep pressing the button to select an Input.