Just an example. Please experiment further yourself.
/* align labels in the middle */
form#dw__register label {
text-align: center;
}
/* The fields aren't aligned anymore, by the varying width of the span with the label texts. Provide a fixed width for equal spacing. */
form#dw__register label span {
width: 100px;
display: inline-block;
/* if the text in the span should be close to the inputfield */
/* text-align: right; */
}