Google Health makes it very easy to download your health data. Just log into Google Health, make sure the profile you want to download is selected, then click on the Download menu at the top of the profile. You’ll see multiple options for different download formats, each appropriate for different uses. See the Google Health help center for more detail on how to download and use the different formats.
Besides downloading your data, you also have the option to share a copy of the data in your Google Health profile with other providers. See the Google Health Copy and Share your Records page for more information.
While there isn't a way to simply import medical records into Google Health, you can get data in by using a number of providers to import records or convert paper records into electronic format. If having bulk import is important to you, please vote on this service on the Data Liberation Moderator page.