POWER: indicates power of course.
LINK (DSL or XDSL): Off means power is off. Flashing means it's trying to train. On means it's trained.
ACT (DSL or XDSL): It flickers indicating activity on the DSL.
LINK (LAN): Indicates whether something with an ethernet card is plugged in, working, and enabled... or not. Also flickers to indicate activity.
10/100M (LAN): On means it's communicating using 100Base-T. Off means it's communicating using 10Base-T.
web interface: 192.168.7.1
factory-default user name: DSL
factory-default password: DSL
Beyond that, read Chapter 4 of the user manual (also linked below).
Quick Setup Guide