You can contact the tenants by offering the apartment for them first. You can offer the apartment when you open the tenant’s profile and click “Aloita keskustelu”. Now the tenant will receive an email and notification of your apartment and can see the details of it. After that you can chat with the tenants in the “Viestit” section when you’re logged in.
The eye symbol next to the message will tell whether the tenant has seen the message or not. If there is a slash through the symbol it means the tenant hasn’t seen the message yet.