After creating a page in the new Google Sites interface, you can add a number of elements to the page, including text boxes and Google Workspace elements such as docs, sheets, slides and forms. Each element appears in a section on the page, and can be resized as required.
To add text to a page:
Click on the Insert tab on the pane on the right-hand side of the screen
Click on Text Box
Type the text you wish to display in the text box
Use the toolbar to format text by changing the style, font and size, or by adding bold, italics, underlining of text colour
Click on the ellipses to show more options including bullets, number and line spacing
Resize the text box by dragging the handles to the left or right