Lubuntu does not change the Ubuntu networking setup, so Ubuntu networking documentation applies to Lubuntu.
Look in the "tray" for Network Manager. It aims for Network Connectivity which "Just Works". Sharing your Lubuntu files has to be done manually. But Lubuntu/PCManFM can connect to existing Samba shares automatically.
A common problem is to upgrade to Lubuntu and lose your wireless connection. We suggest you ask our voluneers in the networking sub-forum of Ubuntu Forums. You will need the model number of your network adapter or laptop, and please be prepared to use the command line.
To change hostname temporarily (until next reboot)
sudo hostname mynewhostnamehere
To change permanently, after next reboot edit /etc/hostname
and also edit (second line, I believe)