Link to Microsoft Flow can be found under Office 365 app launcher. Here is more info about Microsoft Flow plans&pricing.
Sample action #1: send email when a new item is created
Step 5) Select action "Office 365 Outlook - Send an email"
Sample action #2: create event in Outlook 365 Calendar
Step 5) Select action "Office 365 Outlook - Create event (V2)"
Sample action #3: post message on Yammer
Step 5) Select action "Yammer - Post message" and login into Yammer