Hi HalER,
I will try to help you, but I may be too obsolete. I have been running Linux for a while, and dabbling with assembly language for a little longer than that. However, I'm running really old hardware which doesn't have enough memory to run modern Linux. Things have changed a lot, but maybe the old-fashioned ways will still work.
Download
http://www.nasm.us/pub/nasm/releasebuilds/2.11.09rc1/nasm-2.11.09rc1.tar.bz2by default, this goes in my home directory, /home/fbk. May want to go in "/Downloads" for you. I uncompress it right there. You may want to put it someplace else.
tar jxf nasm-2.09.rc1.tar.bz2
(if you're new to Unix, you will be pleased to learn that you can type just part of this and hit the TAB key and it will complete the line) Then:
cd nasm-2.11.09rc1
that should put you in the top source directory - type "ls" to be sure. Then
./configure
that'll ramble on a while and create the proper Makefile - hope it doesn't get any errors! Then... what I usually do is type "make everything" just as a regular user, but you have to be root to install it, so I do "su" at this point (I dont use "sudo" on my old system.
sudo make install_everything
should do it all in one go. Hmmm, that's giving me a bunch of errors. Just go with "sudo make install" I guess. You may be better off to back up to nasm-2.11.08 - it has a known bug with "-f macho64" but is okay otherwise (AFAIK). At this point, typing "nasm -v" should tell you the version and compilation date, if all goes well. You should be ready to start assembling. Got some suitable source? If you have trouble, come back and we'll try again.
Best,
Frank