Thanks for all the messages before but I need your expert help.
I have read the article suggested by @serverco , it is very similar to Get Started)
I have done this to install:
mseleznova@webserver:~$ git clone https://github.com/letsencrypt/letsencrypt
mseleznova@webserver:~$ cd letsencrypt
mseleznova@webserver:~/letsencrypt$ ./letsencrypt-auto --help
After I have made a symlink, as @jpbe advised:
mseleznova@webserver:~/letsencrypt$ ln -s /etc/letsencrypt/letsencrypt-auto /usr/local/bin/letsencrypt
Since I try these steps second time I received reply: ln: failed to create symbolic link ‘/usr/local/bin/letsencrypt’: File exists
But it is not the point.
My problem is that command ‘letsencrypt’ does not work after all these steps. So now I have:
mseleznova@webserver:~/letsencrypt$ letsencrypt --apache
letsencrypt: command not found
Please, advice how to make this command working properly?