Big “pop” type sounds may be reduced with the optional “Pop Mute” plug-in: http://wiki.audacityteam.org/wiki/Nyquist_Effect_Plug-ins#Pop_Mute
Bad parts that are too long for conventional ‘correction’ may be “patched” by pasting a good bit of similar audio from elsewhere over the top of the bad bit. For example: https://forum.audacityteam.org/t/ez-patch/22093/1
As Gale wrote, " Effect > Click Removal" may help if there are many small clicks, but it only works on clicks where the amplitude of the click is higher than the surrounding audio.
“De-Clicker” may help with some types of click sounds:
https://forum.audacityteam.org/t/updated-de-clicker-and-new-de-esser-for-speech/34283/1