You have 3 options:
1. Go to Calendar and click on the red circle at the bottom right corner of the screen to create a new event. Give it a name, choose the date and go to Candidates and recruitments subtab:
Select a person from the list in Select candidates recruitments and click Create. When you later open the profile, you will see this event in the Upcoming meetings.
2. Go to the candidate profile, hover above the red circle at the bottom right and select Add event related to applicant. Fill in the form and click Create.
3. Go to Settings -> Recruitment processes and select a process from the list on your right. Click on the transition between the stages and a new window will pop up:
Give the transition a name and select Add meeting to calendar from the Available actions. Next, click Add and Save:
From now on each time you move a candidate between stages, Traffit will remind you about creating an event. If you click on the message a new window will pop up with an option of adding an event.