Computer Help and Support

Here's one.
https://ubuntu.com/tutorials/command-line-for-beginners

Any command in your path
echo $PATH

-that is executable, will run.
The default includes /bin, /usr/bin and others.
You can create a bin directory in your HOME for personal stuff.

But this might be beyond you until you master the basics, which I recommend.

Otherwise, click on icons like Mac and windows users do. Apps do get installed in "start" menus, but let the package manager do that for you.

You can't skip the basics! It's like driving a car without driver training. Very confusing.

Good luck. Now "hit the books" or web tutorials.