About selection, have you read the last reply you received: How do you trim each end of the recording of a song ?
You run effects from the Effect menu, not from Preferences. However you can’t remove random noises like a whisper or a bang with the Noise Reduction effect - that is only for steady noise like a hiss. Random noises may need dealing with individually according to what they are.
How are you recording voice and keyboard? Both at the same time with a microphone? Can you attach an audio sample of the noises you want to remove? Please see How to post an audio sample.
Generally I suggest you do yourself a favour and make sure you have the current Audacity 2.1.3 release from Audacity ® | Download for Windows.
Then our documentation http://manual.audacityteam.org/ will match with the version of Audacity you are using.
Gale