using link "Install Now"

In my first use of a link (in this site) "Install Now",
locally I was prompted to specify a local program to use,
and I specified apt-get.

Nothing further happened. Then I found in this page
http://linuxappfinder.com/install_info
that apt-url is what to specify.

No more such prompts come from more clicks of link,
therefore I need to know where to clear or change
the above-mentioned specification.