How to change font size for link on widget

around the link you can put this code:

<font size="4">ENTER LINK HERE</font>

I tried that — added your code around the link. No change in the font size of the link.

Sign up here: <font size=”4″>Volunteer Signup</font>

try it both outside, and inside the <a> tag.

another thing you could do in Custom CSS:

footer#footer a {
font-size: 300%;
}

See here for more info about changing font size using CSS

Add this to your child theme’s style.css

footer#footer a {
font-size: 15px;
}