At the main menu click Freeplay and then do Mira HQ.
As soon as the game loads go to the Laptop, open the Laptop and click on Imposter.
As soon as you close the menu open up the sabotage menu and turn off the lights in the office. walk South and enter into storage or the balcony and kill Blue or Pink.
You can then go to the office and turn the lights back on to fix a sabotage you have called.
You do need to load into an online game once and then back out before going to Freeplay.