Go to Television>TV Options>Manage Channels. Then "Right Click" on a Channel and at the bottom of the popup list select "Channel Logo" (Add from File).
You should already have a folder saved somewhere with your saved logos. You have to get the logos on your own. There are some posts here with links to generic logos (you can Google "TV Channel Logos") but many of the logos are specific to your local viewing area, so you need to get those yourself - if you want to have the "correct logo with you Station ID or City:.