how to change font size in wordpress

Go to your WordPress dashboard, then click on Appearance >> Customize >> Additional CSS.

Now add your CSS code in the Additional CSS box.

body {
font-size: 16px;
}

Note: Here I have set '16px' for font size, you can choose a different font size.

If you want to change the font size of a specific headings tags, then add the below code in the Additional CSS box.

h1, h2, h3, h4, h5, h6 {
font-size:32px;
}

To change the font size of a paragraph:

p {
font-size: 25px;
}