I can use Httrack to download public sites when I am not logged in fine but I
get an error when I try downloading sites that require a login and even public
sites won't download for me when I try to login either...

Any help? I already tried following the instructions here but it didn't work :
<https://httrack.kauler.com/help/CatchURL_tutorial>

I can provide screenshots if necessary! It is my first time messing with the
proxy settings on my browser! I used Firefox Developer Edition by the way!