How do I put underline for my clickable text links?

To add that you’d need to add this to your style.css file –

text-decoration: underline;

You would add this to your hyperlinks area. I’m not sure exactly where in your css since I don’t see your link, but it should look something like this –

a {
	color: #ff7632;
	font-weight: 400;
	text-decoration: underline;
}

Do you have a link to your site so I can see your code?

Add this to your style.css file –

.epik-purple .entry-content a {
	color: #000;
}

and you can change the color to whatever you need.