there is option in pppoeconf to automatically connect to internet at startup.
else,
for switching internet on
and
for switching internet off
for icons make on ur desktop or gnome panel launchers by right-clicking on desktop(create-launcher) or panel(add to panel>custom launcher).In the command space type above commands and save.
now for starting internet just click on the icon.also for stopping.
for installing packages use synaptic(menu System>admin>synaptic)