1.) Switching To Or Chaning Your 2.0 Layout
Whether you're switching to 2.0 or adding a new 2.0 layout the first thing you'll need to do is go to "Profile" then "Customize Profile". If you're switching to 2.0 from 1.0 you'll be given an option to make the switch. If you're changing your 2.0 layout you'll be taken to the "Editor"
2.) Clear Old Layout Code.
When you're adding a new 2.0 Code make sure to clear the old layout code first. Go to the "Appearance" section. Go to the CSS section in the Editor, and below the code box you'll see a button to "Clear CSS". Click on that button to erase the old code.
3.) No Theme
After clearing the old layout code make sure "No Theme" is selected. In the Editor window go to "Select Theme" and then click on "No Theme". If you don't do this your layout will look gray and won't appear.
4.) Adding New 2.0 Code
After clearing the old layout code and selecting "No Theme", go back to the "CSS" section and paste your new 2.0 layout code in the box.
5.) Preview
After adding a new 2.0 layout code make sure to preview the layout first. You'll find the "Preview" button in the top left corner. If the layout appears gray or does not appear go back to Step 3 and make sure "No Theme" is selected. Your new layout should appear in the preview window.
6.) Publish
Once you've followed the steps above and have previewed your new layout to make sure it appears correctly, you are aready to publish it to your profile. You'll find a yellow "Publish" button in the top right corner of the page.
That's it. Hope this helps. :-)