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#10
Hello Juan, and welcome to Seven Forums.
Delete the theme that you do not want at the top to leave only the one you want to use. Any changes that you make to a theme that you have already saved will automatically be updated and saved to it. There will be no need to save it as a new theme again unless you just wanted to.
You can also use the tutorial below to be able to save the theme as a themepack as a backup that can be used to restore your theme after a reinstall.
Theme Pack - Create, Save, Install, and Delete
Hope this helps,
Shawn