Please Click on Start a Project

After this Click on Crate from a Scratch

Now Choose your desired Project type, Layout and Paper size then click on OK

Now Add a Text box on Canvas Screen from Text menu

Click on Text size drop-down menu. After click on this a text size drop-down will open

Choose your desired text size then the result of this text size change can be seen in Text-box

In same way Click on Text size drop-down menu after add a Headline on canvas screen. After click on this a text size drop-down will open