I must be blind - I couldn't find anywhere in the A - Z guide anything about using italics in your story.
I personally use italics for emphasis. Bold & underline ruin a story IMO.
Well, from my experience, I can tell you that the following are acceptable uses of italics when posting here.
Emphasis on a word or phrase.
Thought dialogue ( character's thoughts )
Setting off something such as a note someone is reading in the story.
That's all I can think of off the top of my head.
If you're talking about how to use italics in your story, highlight what you want to be in italic with your mouse. Then click the italic button at the top of the story text window.
The use of italics in English grammar is fairly well-defined.
They should be used for a title: name of a book, story, movie, television show, artwork (painting or sculpture), well known speech or address, plays, and longer musical compositions [so Modest Mussorgsky's Pictures at an Exhibition would be italicized, but the names of the individual components of that composition (Bydlo, Limoges, Samuel Goldenberg and Schmuyle, etc.) would not be].
(Although, I got into the habit years ago of using both italics and underlining for such things because it was in common use then. And really I should try to get away from it, but the mental rut seems to be too deep.)
Italics can/should be used for emphasis.
For the name of some sort of vehicle/transport: Titanic, Mustang, Twentieth Century Limited.
You'll often see it used for a word used to convey a sound: boom, smack, splash.
It is used for some foreign words. The most common usage seems to be that a foreign word that is well-introduced into English usage would not be italicized (like et cetera), but foreign words or phrases less used would be rendered it italics (bon mot, maître d') - obviously there's a lot of judgment and subjectivity on the writer's part about what is or isn't in common use.
They can also be used for a number or letter that represents itself: The building had a big C written on its side.
Italics is also used to render a character's interior thoughts (when presented as internal monologue). Although there are differences of opinion as to what method to use. Some prefer italics. The other way to do it is with the words in single quote marks. (But never italics in single quotes). Some think italics best and some single quotes. I favor and use italics, although I think there are positive arguments to be made for either. I like italics because once a reader knows you use them in this way they are the quickest and surest way to render character thoughts and have the reader recognize them as such. Also, italics lessens the need for a dialogue/thought tag (, she thought.)
Hope the information is helpful.
"hmmm, I must give this more thought!" he thought.
I have to agree on the long blocks of italics ( even though I've done it in the past )
Many ( perhaps even most ) readers may not blink an eye, but for others, trying to read a lot of italic text is serious eye strain.
I've purposely avoided this in recent years, finding ways to break up those long blocks with action in narrative and such.