Yes, VL is a little simpler than the "fully automatic" distros that grab the headlines. You need to open the hood and get your hands dirty to really appriate it. As far as this command goes, you would add the line:
echo 10 > /proc/sys/vm/swappiness
to the end of /etc/rc/d/rc.local
The commands in rc.local get executed with root privileges. Commands in your WM/DE startup files launch with user privileges.
Actions performed as regular user can bork your profile, but won't hurt the system, so keep a good backup of important files and go for it. Have fun figuring things out.