These types of errors are normally caused by misconfiguration of your /etc/apt/sources.list.
In this example on Debian 10, if you didn't complete the install correctly, you will have no repos enabled and only rely on CDROM.
"Package wget is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source.
E: Package 'wget' has no installation candidate".
In the case of Debian 10 here is what you need to add to /etc/apt/sources.list
deb http://deb.debian.org/debian/ buster main
#If you are using another Debian then you would replace the above with the repo URL of your distro and the codename Buster with the codename of your release contained in /etc/os-release "VERSION_CODENAME"
You could also add on "non-free contrib"
sudo apt update
sudo apt install wget #or the missing package
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