Hi.

Tired of lengthy manuals about ADSL setup, here is a copy+paste (with a bit of editing) from an email I’ve sent once (year 2005).

apt-get install ppp pppoe

### summary of changes ###
file /etc/ppp/options:
    change "auth" to "noauth"
    add "plugin /usr/lib/pppd/2.4.3/rp-pppoe.so"
file /etc/ppp/pap-secrets:
    "MYUSER@MYPROVIDER" * "MYPASSWORD" *
file /etc/ppp/peers/dsl-provider:
    "user" -> "MYUSER@MYPROVIDER"
    on line with "pty" - change eth0 to correct interface
        (eth1 in my case, but should usually be eth0)

manual start:
    pppd call dsl-provider
auto start:
    file /etc/network/interfaces:
        ###
        auto ppp0
        iface ppp0 inet ppp
            provider dsl-provider
        ###
### end of changes ###

Use at your own risk.
Hope that helps.