To install a tarball, the steps are usually to extract the file as Carmar explained above. Then you can open a terminal in the directory which there are many ways to do. With my file manager, I can right click anywhere in the window and select "open in terminal". It is also a button on the toolbar I can set in settings to be present.
Or, hit the keys ctrl+alt+t and then use the Change Directory command
cd
If you downloaded a file, then it would land in your Downloads folder, same as it does on your average Android phone. So just typing the path, including the exact name of the folder you just extracted, is the change directory path.
For example, if I downloaded and extracted gimp2.10.8.tar.gz, I would extract it, then cd to
cd ~/Downloads/Gimp2.10.8
The "~" is terminal shorthand for Home Directory in the path. At this point, the installation steps would be
/.configure
make
sudo make install
Which would be using the software named "Make" to run the installation.
We did not name the thing.
While these steps look involved in long typed out form, after doing it a couple times, like riding a bike, it becomes familiar and easy.
All of that said... Most things folks are trying to install these days are not packaged to be built from source except things intended for experienced Linux users or developers. Many users new to Linux will look for a needed piece of software and be led to a package that is a tarball that is no longer being maintained or is old... and run into dependency problems. And since this is a New Method to that user for installation, it can get very confusing. You almost wish that maintainers would leave a note when they stop maintaining something with the date on it saying, "Sorry, we are closed."
So as Carmar asks above, knowing what you are trying to install can help us figure out the best way for you to address your installation.
The majority of packages folks are looking for these days are in a Repository, so installation requires only that you run Advanced Package Tool (apt) to install the software.