The workshop venue provides wifi access for all participants. If you have an eduroam account, you can use that, otherwise reception will provide account details. Those who stay at the Harnack House overnight will receive the access code with their welcome letter.
Use the local public transport (BVG) website for information and time tables. The closest stop to the Harnack Haus is on the line U3: Freie Universität (Thielplatz).