It’s ok if you haven’t connected to the Internet yet. Check out the below page on Xbox.com for details on how to connect to Xbox LIVE.

Xbox.com Home >Support > Xbox LIVE > How to
http://support.xbox.com/en-us/xbox-live/how-to/home

Refer to this page if you don’t know how to connect to the internet.
Once you’re connected, move on to STEP 2!

Press the Xbox 360® Xbox button, and select Game Marketplace from the Marketplace tag.
*A profile with an Xbox LIVE Gold Membership or Silver Membership is required to go access the Game Marketplace. Make sure you have a membership before connecting.

If you’ve reached the Game Marketplace, you’re ready for STEP 3!

Select “Demos” to see a list of downloadable demos. Select “New” and then look for “REAL STEEL Trial Version”. If you can’t find it by selecting “New”, try sorting by “Title” and going to “R”.

Once you’ve located the “REAL STEEL Trial Version”, go on to STEP 4!

Select “Download” and advance to the confirm purchase screen. From there, select “Confirm” to begin the download.

Once the download completes, you’ll be ready to play the REAL STEEL trial. Now on to STEP 5!

Press the Xbox 360® Xbox button, and select Game Library from the “Game” tag. Select “REAL STEEL” from the list to play the free demo!

The REAL STEEL Trial Version includes offline multiplayer mode, where you can control the robots from the film (Atom, Noisy Boy, Metro, and Midas).
Now prepare yourself for the thrill of robot boxing!!