Crescendo in Cubase Elements 11

For a single note, how can I increase my dynamic/velocity from piano to forte/soft to loud within the same note?

Play it stronger?
Very unspecific question.

Either see if the instrument responds to expression or fade out with controller 7 which is volume.

What is this? Or, a better way to ask this is, how can I find it?

How do I crescendo in Cubase Elements 11.

Controller 7 is volume. Look at the bottom of grid editor where there is a drop down where you can choose your controller and draw in a curve. You can even use automation on the slider in the mixer

How do you crescendo this on a piano? Or a guitar? …compared to a trumpet or a violin.

It depends on the (VST) instrument how exactly you can make a held note gradually louder.