Can someone tell me how to write the note as in the red circle with Musescore 3?

N - enter note input mode
3 - set note duration to sixteenths
F, Shift+A - enter the first F/A chord
R - repeat the last chord (enters the second F/A chord)
D - enter the D
E, Shift+G - enter the E/G chord
N - exit note input mode

Click on the D to select it. Now press Ctrl+ Shift+Down. This will move it to the bass clef.

It also places the beam between the treble and bass clef notes. Select the beam and drag it back above the treble clef notes.

Oh, I see that I have a 4/4 time signature so the rests in the measure aren't the same. Nonetheless, that's how to do it. For more info, see https://musescore.org/en/handbook/4/cross-staff-notation.