I attached my HDMI cable to my Samsung Tv. The "classic" apple screen comes up, but not the screen on my MacBook. Therefore I can't access my laptop.

Turn on AirPlay Mirroring: About AirPlay Mirroring in OS X Mountain Lion

If you are not using Mountain Lion: How to use multiple displays with your Mac

You have the display set in Extended Desktop mode with the MacBook as the main screen. The Menu Bar and Dock will be on the MacBook display and your background screen on the TV but you can move the cursor onto the TV screen.

In System Preferences>Display on the MacBook screen there should be an Arrangement tab when you have the MacBook hooked up to the TV and both screens working. When you click the Arrangement tab do you see two monitors side by side? One of them will have a Menu Bar at the top. Just click on the Menu Bar and drag it to the second monitor. That will make the second monitor your main screen.

The TV will now have the Dock and Menu Bar and windows will open on it. But you can move the cursor to the MacBook screen and move windows from the TV over to the MacBook screen.

You can now use your MacBook in Clamshell Mode with a wired or Bluetooth keyboard and mouse. http://support.apple.com/kb/HT3131 When you disconnect from the TV your Menu Bar will automatically change back to the MacBook.

Or if you want to work on the MacBook screen while showing it on a TV you can check the Mirror Display box on the lower left hand side of the Arrangement tab under the two monitors box. That will give you the same screen at the same resolution on both the MacBook and the external monitor.