The freeroam app is available on the smartphone. Top left, then the blue pin icon.
The app shows you what's available to do in the freeroam area or what is required before you can move on.
If you're just starting the game, you need to click on the window by the computer/chair to spy on Karla. This is to highlight this feature is available. The spy feature is generally optional after this point unless something in the story requires otherwise.
If you're at the end of the first day, There are some more tasks, such as a message on the phone you need to respond to and a task on the computer that needs to be completed.