In the office(starting scene), P to reload your pills (filling the bar on the left in the immune system(second scene), which you should not see until you enter it) click SPACE to enter your immune system(takes 2 seconds) where you can place pills with LMB at your mouse position, and the press SPACE when in there to return back to your office for reloading(P).(the viruses can still merge when in the office, and you could lose there, so as quickly as you can, return back to the immune system and carefully place your pills. You lose if two blue viruses combine with each other.