Aligning knewsbutton field

I’ve never used knews, but I’ll have a go.

Try adding these CSS rules in a child theme or custom CSS module of Jetpack

.knews_add_user fieldset {
	padding: 0;
	margin: 0 0 0 10px;
	width: 100%;
	float: left;
}

.knewsbutton > input.knewsbutton {
	padding: 4px 0;
	width: 210px
}

I’ve only looked at this in firefox, so you may need some tweaks to make it look pixel-perfect in other browsers, but hopefully this will give you a starting point.