I'm not sure what you mean by "channel store", but if you are wanting to download and install apps, go to the Market from the main home screen.
If you're wanting live TV channels, they cannot be purchased through the Market. You have to purchase a subscription through a third party and enter the server information the third party provides you in the "settings" section from the home screen. Once done then you go to Live TV on the home screen and the channels load up from the server you entered in the settings.