I'm just a silly billy who has lurked on Chapo.chat wink for quite awhile now; But I don't know how to do half the things (more like 90%) above the text box window that I put my delicately selected words into to make the freshest and most delectable word salads. So... How do and what do? If a power poster would like to go over each feature individually I shall abandon atheism and pray to satin for infinite 9/11's on the first world. Thx in advance. (this was going to be in regards to the emojis but thankfully realized that it wasn't just the lame ones you get on your phone when you click on the face, only if you don't search for anything) 
The toolbar above the text box is pretty self explanatory for most things. Bold and italics are the B and I. You can either highlight the text you want and then click the button, or click the button to enter the modifiers (or just type them in yourself.)
The chain is for making links, text first in the square brackets, url second in the parentheses.
Smiley is emoji (we have the best emoji, folks.) Sometimes our custom emoji are slow to load, just give them time.
The picture of the mountain and sun is for uploading images (you can also generally paste images in.)
The H is for headings, which would make the line have big text. This hasn't worked for me since at least the couple of updates leading up to federation, the system that allows us to interact with posts on lemmygrad and other instances.
Strikethrough is the S with the line through it, you seem to have figured that out! Nice! Works similarly to bold and italics.
The quotation mark allows you to do...
You can use a hyphen to make a bulleted list like so:
Make sure you put a space between the hyphen and the text you want bulleted. Also make sure to hit enter twice to break up your lines, otherwise they won't actually separate.
tick marks ( use the <> button) allow you to write in monospaced font like this without formatting, useful for code or other situations.The subscript and superscript buttons which look like x'es with a little text cursor down or up, allow you to make small text low or high. Also handy for math stuff. 69
The triangle with the exclamation point is for spoilers or other collapsed text.
it does this, click on me
You leave the first time it says spoiler, but can replace the second time it says spoiler to change the heading text. The second line of dashes, you can put the inner spoiler or collapsed text.
Don't click the question mark in the circle or it will delete your post and take you to the help page.
Also you can use a backslash (\ this guy) as an escape character to be able to post a modifier character, like so: ^
I recommend hitting the preview button before posting just to double check that everything worked right.
Edit: I figured out the quote line thingy whoop whoop. A big thank you to the comrade who let me know it's the right pointy carrot with a space after it.