It can be helpful to copy and paste the text below into a sandbox, and apply all of the options directly to this text to see what it does.
Paragraph: This helps you set the style of the text. For example, a header, or plain paragraph text. You can also use it to offset block quotes.
A: Highlight your text, then click here to format it with bold, italics, etc. The "More" options allows you to underline, add code snippets, and change language keyboards.
Links: The chain button allows you to link your text. Highlight the word, and push the button. VisualEditor will automatically suggest related Wikipedia articles for that word or phrase. This is a great way to connect your article to more Wikipedia content. You only have to link important words once, usually during the first time they appear. If you want to link to pages outside of Wikipedia (for an "external links" section, for example) click on the "External link" tab.
Cite: The citation tool in VisualEditor helps format your citations. You can simply paste a DOI or URL, and the VisualEditor will try to sort out all of the fields you need. Be sure to review it, however, and apply missing fields manually (if you know them). You can also add books, journals, news, and websites manually. That opens up a quick guide for inputting your citations. Finally, you can click the "re-use" tab if you've already added a source and just want to cite it again.
Bullets: To add bullet points or a numbered list, click here.
Insert: This tab lets you add media, images, or tables.
Ω: The final tab allows you to add special characters, such as those found in non-English words, scientific notation, and a handful of language extensions.