Web to the Nmap home page.
Click on Download. Save it in
/usr/src.
(as root)
cd /usr/src
gunzip nmap-2.53.tgz
tar xf nmap-2.53.tar
rm nmap-2.53.tar
cd nmap-2.53
./configure
make
make install
make clean
The main doc is the man page, but there are some HTML files in the distribution:
(as root)
nmap -sP 128.117.8.0/24