the F Major chord
It is often the case that a triad chord name is built by taking the tonic, lowest note in the chord, and adding its mode, Major or minor. For example, take the C Major chord (C-E-G) you recently learned. But just to keep you on your toes, this is not always the case. Sometimes the tonic is not considered to be the lowest note on the scale. In this lesson, we'll look at an F Major chord which is comprised of C-F-A. But just be aware that an F Major chord could also be F-A-C. It was mentioned in the previous lesson (on G7 chords) that chord naming is complicated. And again, not to get bogged down on this now, you will find a more complete discussion of the complications to chord names here (spoiler alert, where you find that C-F-A is called the F Major chord's 2nd inversion).
When playing this chord with the left hand in the C position, it's now the thumb that stretches to the right from the G key to the A key. The other fingers remain in place and it's played with the pinky, middle finger, and thumb.
Here's how it looks on the staff. Hopefully by now you can see the interval count between the first two notes is 5 (there some space between the noteheads). Between the 2nd and 3rd notes the count is 4 (noteheads are touching).
First, practice switching between all three chords that you have been introduced to so far: C Major, G7, and now F Major. And with the usual learning approach, start with this version of "When the Saints Go Marchin' In" where the chords are played with the left hand and the melody with the right hand. The video.
In this tune, some of the note durations span a full measure and sometimes at the end of a Grand Staff line, they continue onto the next line. To make this more obvious, the notetail at the end has a little triangle outside the staff line as in measure 4.