If you're burning it to a DVD, insert your DVD, select the disk image in the sidebar, and hit the 'Burn' button. Open up Disk Utility and drag the DMG file into the left-hand sidebar.
Navigate to Contents > SharedSupport and look for a file called 'InstallESD.dmg'. Right-click on the installer and hit 'Show Package Contents'.
The installer should show up in your Applications folder. On a Macĭownload Lion from the Mac App Store. However, the other option is to use a Virtualbox VM to run OS X temporarily (scroll down for that info). As far as I know, the only way to properly create a bootable Lion disc/disk is to use Disk Utility on a working Mac.