It's a good idea to back up (Export) your Customizations on a fairly regular basis - after you create or alter any of your Entities, Workflows, etc.  This is a very simple process that can make your live easier in the future.  If you are just getting started with CRM Live, go ahead and create a baseline export of the pristine system.

1. Navigate to Settings -> Customizations -> Export Customizations.
2. Select More Actions -> Export All Customizations.
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3. You may get an Internet Explorer warning.  Click Download File. 
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4. Don't be surprised if your only result is that you go back to your main Workplace screen.  Simply repeat steps 1 & 2 above and I expect you will be successful
5. Give the customization.zip file a logical name and save it to a location that has strong backup procedures in place.

If you ever find yourself in need, you'll find you have the XML to restore your customizations to a prior state.