How can I get MacKeeper out of my Mac machine & others

ist: MacKeeper Helper got into my machine trash and obstructed me from emptying my trash, which is accumulating. Each time I empty my trash it says 'Mackeeper Helper is in use' Why did it want to get into my trash and how did it? I downloaded MacKeeper in April of 2013 and later never touched it. I did not understand what it was for and don't need it. I am a 80+ senior and very very hard of hearing who couldn't understand all this new technology. I just wanted a computer to communicate with the few friends that I have. I have other problems too.

2nd: I think it was in 2009 or 2010 (the time when the large desktop computer just came on sale), and added another year of warranty and also joined the class to learn about computer. When the warranty expired at end of 2012 Google popped up asking for the password of IMAP & SMTP. Nobody told me that I should remember that, and so got into trouble. I, having no one to help, went on the net to search for help about restoring my SMTP (outgoing mail) password. Mac Technical Support 1st it was under the name of USFIX TECHNICAL SERVICES (I paid $99.99. ("payment" <payment@usfix247.com>. When I called again it came under a new name of "Pairsys Inc" <pay@pairsys.com> telephone #855-786-4335 I paid $299.99 for 1 year. But in October the MacKeeper got into my trash and the SMTP password was refused again. I can only receive mail but cannot send out.

3rd. : Mail & MacKeeper wanted access to my keylink password, which I never knew I had one, and one day mistakenly clicked on the keylink (out of curiosity) to see what it contains and locked it..

Now I am in a mess. It all started with the SMTP password.