Ribbon > Edit > Font

The Font group makes font, highlight, and other style effects available.

An alternative is to use the Font Dialog: Right-click > Font.

Font Open: Change the Font dialog box. Change the Font size

Bold: Make the selected text bold.

Italic: Italicize the selected text.

Underline: Underline the selected text.

Strike: Draw a line through the middle of the selected text.

Subscript: Create small letters below the text baseline.

Superscript: Create small letters above the line of text. To create a footnote, click Insert Footnote on the References tab.

Increase: Increase the font size.

Decrease: Decrease the font size

Increase and Decrease only work if font size is explicitly set in your document.

Font Color: Change the text color.

Highlight Color: Highlight text as you read. Make text look like it was marked with a highlighter pen.

Double-click on the Highlight  button to go into highlight mode.

Clear Formatting: Clear all the formatting from the selection, leaving only the plain text.

Clear Formatting does not in all cases clean the HTML code. If ot doesn't, the alternative is switching to HTML code view.
Using the ribbon