To make a copy of the file use:
cp /etc/ushare.conf_sample /etc/ushare.conf
In terms of editing, the 'vi' editor is supplied as standard, but is certainly not friendly to use like many unix/linux editors. I would suggest instead the 'nano editor which can be downloaded from my web page and installed using a command of the form:
tar -xzf <path-to-downloaded-tgz-file> --directory=/usr/local
where <path-to-downloaded-tgz-file> is to where you put the file you downloaded - and is probably something like /mnt/array1/share/nano-2.2.4_ppc.tgz if you put it into the root of the default share.
After nano is installed you can use
to edit the file. nano includes an on-screen help to the less obvious commands so you should be ok from there.
You might find it useful to grab a guide to common linux/unix commands (e.g. ls, cp, cd etc) to make it easier to do standard things from the command line. There are plenty around on the internet.