Follow that URL. This is probably a quick and dirty solution, but I am fairly certain that it will get done what you want to get done as far as executing that file. Essentially you will have to use the command line and enter the
directory to your list of environment path variables.
Your list of environment path variables is a list of directories that, when you tell the shell to execute a command, the shell goes and looks in your directory tree according to the list of path variables (directory paths). It's like giving your shell places to look without it having to ask you where to look, whenever you tell it to execute a command. I would recommend reading that entire page before you edit your path.
And I have to state that there is a minor fault in the text of that web page (from the URL above).
The fault is that it doesn't show your prompt. There are situations when you want to do this as normal user, and then also as root user (admin user). Search and read around for this to know exactly what your present usage requires. There is plenty of material on the Net on this.
If I am not mistaken your command line should look like, for example, the following if you are going to put your /steamcmd directory at the beginning of the path.
And then you may have to export it.
I would try to do this as normal user first.
Editing your path as root, su, or sudo may edit your path exactly for those purposes, and not for purposes of normal user, eg. user "aras".
and you will find another page explaining this process, maybe a bit better. In fact, if you google for
how to edit path in linux
you should get enough material to get your problem solved.