I taught Basic Computing, so see if this helps:

"Hold the Fn key together with F6"

Your keyboard, bottom left, has a row of special keys, including CTRL (or Ctl), Fn, Windows icon (for the Windows menu), Alt, Spacebar, then another Alt and Ctl.

The same way you hold down the Shift key, to get a capital Letter, the Function, Alt and Ctl keys are the same, as an optional trigger, and then you use another key with them in sequence. I had many students that would try to Poke both the control key and the operational key at the same time, but no human can make that happen. Example: Ctl+1 is typically Help in Windows-compliant programs, so you hold down Ctl and keep holding it while you poke the 1, then let go of Ctl.

Look at your Dell keyboard to see the text on the keys is typically in two colors (likely not only in the Function key row), when there are two functions or operations. For instance, a number pad with NUM LOCK OFF, has the "other" functions, of mouse control, page up/down, Home, etc. So,my Dells have different functions. You might need to hold down the Fn key and then the F functions work, or the alternate functions work. One of mine is blue text for the Scrl Lock, the touchpad lockout, the WiFi lockout, and the Fn key also has blue "Fn" on it.

Lastly, my newer Dell (Alienware) has a block of Function keys to the left and also across the top of the Number pad. These are called Macro keys, not Function keys. They are numbered 1-9. They are not the same as Function keys. Function keys are hardcoded to their functions. Macro keys are ours to program. I have a set I coded for volume up/down/mute, because they are easier to hit, when the phone rings and I need to take that call.

Hope that helps.