How to install that .deb from a .tar file

Eventually you’ll forget.

It’s an idea to go through the README file. Configuration flags exist in those sometimes, but usually cd-ing into the DEBs folder is what’s needed. Try this

tar -xvf "fileInQuestion_x86-64-debs.tar.gz"
cd "fileInQuestion_x86-64-debs"
cd DEBS
sudo dpkg -i *.deb

at which point typing

which "programName"

might be wise should you decide to do something about your old variable path. From the first code block, the -xvf variables simply mean eXtract, Verbose (display action on terminal), and File archive. Note that installing a program by the DEBs method has a probability of changing a configuration or a path variable somewhere. You will not notice the effect until maybe two or four years into the future. It will probably happen when you upgrade your machine to the next major version. Try not to update things during study week or before a big presentation.

Have fun!