Now you can input the dynamic markings. These are inputted with a special note called a "spacer," that uses the letter "s" rather than a note name. You can also use rests (both partial- and multi-measure, r and R), but dynamic markings cannot be assigned to them.

For example, if you want a piano marking on the first beat, and a diminuendo from the third to the fourth beat, you could write this: s4\p r s\> s\!, or this: s2\p s4\> s\!

That's all there is to it! Think of the dynamics part as an invisible, pitch-free line between the two staves, for the sole purpose of dynamics (and other expression markings).