Add subsection about how to click symbols, signs, and other objects

[daobrien]

From team discussion:

For things that you click (+ or ^ or whatever) use and include the object type:

• Click the + sign
• Click the ^ symbol

Note that this is different from what we do for buttons in most cases.

Need to find a logical place to put this; perhaps somewhere related to "symbols"?

[daobrien]

Might fit here: 3.4. Documenting the User Interface