You need to follow a specific set of steps when connecting your Canon Rebel t5i to your computer. Otherwise, you can damage the camera or the memory card. Here's the suggested process:
Make sure the camera battery is fully charged.
Running out of battery power during the transfer process can cause problems, including lost picture data. Alternatively, if you have an AC adapter, use it to power the camera during picture transfers.
Turn your computer on and give it time to finish its normal startup routine.
Turn the camera off.
Insert the smaller of the two plugs on the USB cable into the A/V Out/Digital port on the side of the camera.
This port is hidden behind the little rubber door that’s just around the corner from the left side of the monitor.
Plug the other end of the cable into a USB port on the computer.
Turn on the camera.
What happens next depends on what software you use to download photos. As for the camera itself, it doesn’t give you any indications that it’s in transfer mode, aside from a brief flicker of the card access lamp. If you try to focus or take a photo, the word “Busy” appears in the viewfinder.