Use the subscript formatting option in your editor or app
In HTML, wrap the text with `…`
In LaTeX, use `_{…}` for subscript
In Microsoft Word, select the text and press `Ctrl` + `=` on Windows or `Cmd` + `=` on Mac
In Google Docs, select the text and choose Format > Text > Subscript
In plain text, use an underscore before or after the character if supported by the context
In Unicode, use subscript characters when available