The chords in Figure 5.1 are written in root position, which is the most basic way to write a triad. In root position, the root, which is the note that names the chord, is the lowest note. The thirdof the chord is written a third (Figure 4.26) higher than the root, and the fifth of the chord is written a fifth (Figure 4.26) higher than the root (which is also a third higher than the third of the chord). So the simplest way to write a triad is as a stack of thirds, in root position.
Write a triad in root position using each root given. If you need some staff paper for exercises you can print this PDF file.