Change header size on footer only

Hi, I added a newsletter function on my footer but I find the heading too big. Is there a way we can decrease the size? I've added this code but got no luck.

Footer.Footer h2.newsletter-form-header-title {
    font-size: 13px;
}
@media screen and (min-width:641px) {
footer.Footer .newsletter-form-body {
    display: flex;
    flex-direction: row !important;
}
}

Hi. What is site url?

My site is not live yet. This is the built-in domain: tulip-hen-x9ws.squarespace.com
The password is: kwalityskye

6 hours ago, ReenaD10 said:

My site is not live yet. This is the built-in domain: tulip-hen-x9ws.squarespace.com
The password is: kwalityskye

Add to Design > Custom CSS

/* newsletter */
.sqs-block-newsletter .newsletter-form-header-title {
    font-size: 12px !important;
}