The department liaison for international services is Amanuensis Ellen Mustonen, office D237, phone 191 51383, email ellen.mustonen[at]cs.helsinki.fi
The International Staff Service, email int-staff[at]helsinki.fi, is responsible for international services for the whole university.
The following link contains information on e.g. residence permits under 'What to do before arrival: permits and documents' and 'Things to take care of when in Finland.'