you may need a little more experience in linux before jumping right into configuring samba. first to answer your question, you should use a notepad tool called "vi" but, i don't want to explain to you how to work it. search google if you're interested, an easier way is to type
cd /etc/
; this will put you in the samba config dir
pico samba.conf
; this will run pico, an editor like vi, on a blank file called samba.conf
what you should be doing anyway is using an example .conf file, which is included in your copy of samba. run vi (or pico) on that file and edit what you wish, and make sure it ends up in /etc/samba.conf (cp original.file /etc/samba.conf)