Place your index finger across all six strings at the 1st fret
Place your middle finger on the 2nd fret of the G string
Place your ring finger on the 3rd fret of the A string
Place your pinky on the 3rd fret of the D string
Strum from the low E string down
Keep the index finger pressed firmly to make the barre clean
If needed, start with the easier F major shape using only the top four strings
Move the shape up and down the neck to play other barre chords