Nessus is security and network related program so I decide to put my question here........ HOW CAN I INTALL IT!!!!!!????
I have downloaded source from packetstormsecurity.com, it contained 4 tar.gz and MD5, I installed everything, then as written: nessus-mkcert
And it says can't find some library, and: "Make sure your library loader is configured properly and that nessusd is in your $PATH.." I can start nessus, but I am wondering what that expression above means? And why I cannot start 'nessusd'.
thnx

I have found out that I cannot start scan if nessusd is not running.
How can I solve such problem?
thnx

Nessus is security and network related program so I decide to put my question here........ HOW CAN I INTALL IT!!!!!!????
There's your first problem, wrong diagnosis. You have probs installing the app, and not security related issues with the app or functionality: so it should be in either /general, or /software.

And it says can't find some library,
What library? Why not show some errors?

and: "Make sure your library loader is configured properly and that nessusd is in your $PATH.." I can start nessus, but I am wondering what that expression above means?
execute this: "ldconfig -p -v" and see if the library you installed is mentioned there, else you will I. have to add the path where you installed the library in /etc/ld.so.conf or II. if the path is there, update the cache running ldconfig.
Now execute "echo $PATH" and see if nessusd is installed in one of the dirs mentioned there, if not, move it there.

//Mod.note: moving to software.

unSpawn I made 'ldconfig -p -v' as you sad, so nessus-mkcert began to work, it wants to create some SSL Sertificate
Now the configuration begins.............

I have created certificate.....then I wanted to adduser:
Login: nautilus
Athentification (pass/cert) [pass]: `I write my password here`..
And then such line appears again and again...How can I complete it?

Please read the docs before you configure, compile, install.
The man page you're looking for is man (8) nessus-adduser.

www.nessus.org has all the docs you need.

a couple basic commands to get you going:

nessus-mkcert
nessus-adduser
nessus-update-plugins

before you launch nessus, make sure nessusd is running or you will not be able to login - $nessusd -D