To learn how to use Notch Filter and Equalization, see the Manual: http://manual.audacityteam.org/man/notch_filter.htmlhttp://manual.audacityteam.org/man/equalization.html
The best way to learn is to try.
Preview the results at different settings. Look in Plot Spectrum or Spectrogram to see how different settings change the frequency distribution. Ruler Of Time (1.06 In Question).wav:
I only hear the slightest hint of a click, masked by "fizzy" sound. For such a short length, you can use Repair or Delete. If you are editing a video and going to add the modified audio back to the video, then of course you can't delete. Repair removed the hint of a click that I heard. Another Weird One Amped.wav:
If you mean the slightly fizzy distortion at about 0.7s, it looks like there are lots of overtones in the spectrum and I would guess it is part of the recording - it just sounds like that. If this was a file from YouTube, it will be a lossy encoding of the original CD, which could add phasiness, fizziness and all kinds of distortion. If you use the menu by the Track name, choose "Split Stereo Track" then Solo the right channel to listen to that channel only, do you agree that sounds cleaner? If so, that points to using the right channel content in the left channel. You could do that with Steve's Channel Mixer: http://wiki.audacityteam.org/wiki/Nyquist_Effect_Plug-ins#Channel_Mixer
As well as being past my aural prime, I am not an audio engineer. I will now leave this topic to those who are in-prime, audio engineers.