In contrast to how slow the icon appeared on the screen, it vanished into a small underscore in the top left.

Seems like the device is waiting for an instruction. However, you have no idea what to type into the keyboard. Fortunately, the one installed seems to be using a standard QWERTY Keyboard, so you should not be as unencumbered as you thought you could be.

However, your typical behaviour may be useful here, considering your lack of social skills. Seems like you prefer the comfort of the cold and mechanical to soft fleshy meat things anyway.

Luckily for you, you are quite experienced with handling old equipment like this, and inputting extremely direct and forward instructions should come fluently to you.

Regardless, you probably should input an instruction.

Considering you have no idea what is installed on this Operating System (assuming it is one), and if you broke this thing you would surely die of boredom in this isolated room so, the safest option would be to Boot the OS.