First of all, install GoAccess. It's avalaible through the Raspbian repositories.

apt-get install goaccess

Now uncomment the following lines from the GoAccess config file /etc/goaccess.conf, using your favourite text editor.

emacs /etc/goaccess.conf

date-format %d/%b/%Y
log-format %h %^[%d:%^] "%r" %s %b "%R" "%u"

These lines set the default date format to Apache format and the default log format to NCSA Combined Log Format, both used by the NGINX logs. Now, test GoAccess with current NGINX log file:

goaccess -f /var/log/nginx/access.log

And if you want to process all gzipped log archives (this may take a while), use this:

zcat -f /var/log/nginx/access.log* | goaccess

Important: Note that all commands are executed as root. If you do not have access to a root shell (by default you are not allowed to use it), use sudo to execute them (prefix all commands with "sudo").