The apartment is normally available from the first day of training. Unless you have arranged otherwise with your employer, you should find your way from the airport and to your apartment by yourself. Keep your ticket because it's valid for transfers to other buses during the next hour. The Finnair bus is more expensive and the ticket has no right for transfer. One of the things you will need to do after arriving is to open a bank account , which is necessary for your salary.
Several banks operate throughout the country.
Salaries are usually paid at the end of the month, so have enough money with you. For currency exchange smaller bureaus like Forex and Finex are often cheapest.