how do i delete software?

We know it's junk (and we consider it malware). To uninstall the application, just open Finder, select Applications on the sidebar and drag MacKeeper to the Trash. Finally, empty the Trash. See > http://applehelpwriter.com/2011/09/21/how-to-uninstall-mackeeper-malware/

Also, see > https://discussions.apple.com/docs/DOC-3036

Probably wouldn't hurt to delete its preferences if there are any: Home Folder_Library_Preferences

That step appears on the link I provided on my first comment

I know. I just remember when I was first trying to figure all this out that sometimes repetition never hurt;)