Open Calendar in the sidebar (on a phone, in the bottom bar).
At the top you see Upcoming events and Overdue follow-ups. The calendar shows three kinds of dates from your applications:
Follow-ups you've set
Application deadlines, while the application is still Saved
Interviews you've logged
Select a day to see its agenda. Each event has icon buttons:
the arrow icon opens the application and its resume and letter tools
the tick icon marks a follow-up complete
the microphone icon starts practice for an interview
Choose Today to jump back to today.
Add dates
Open the application in Applications, then:
Follow-up: set Next follow up, or use the bell icon on its card.
Deadline: set Deadline.
Interview: open Log an update, set Activity type to Interview, pick the date and choose Add to activity.