Try replacing the code inside the Processed Form Code field with the one below:
<form action="//eyecandypopper.us8.list-manage.com/subscribe/post?u=effbdcf154311f0fe1a6c2874&id=5b57364acd" method="post" id="mc-embedded-subscribe-form" name="mc-embedded-subscribe-form" _lpchecked="1">
<div class="mab-field">
<label for="mce-EMAIL"><span class="asterisk"></span></label> <input type="email" name="EMAIL" id="mce-EMAIL" placeholder="email*" style="background-image: url("data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR4nGP6zwAAAgcBApocMXEAAAAASUVORK5CYII=");">
</div>
<div class="mab-field">
<label for="mce-FNAME"></label> <input type="text" name="FNAME" id="mce-FNAME" placeholder="first name">
</div>
<div class="form-dates">
<label for="mce-MMERGE3-month">Cleanse Start Date <span class="asterisk">*</span></label>
<div class="mab-field">
<input type="text" pattern="[0-9]*" placeholder="MM" size="2" maxlength="2" name="MMERGE3[month]" id="mce-MMERGE3-month">
</div>
<div class="mab-field">
<label for="mce-MMERGE3-day"></label> <input type="text" pattern="[0-9]*" placeholder="DD" size="2" maxlength="2" name="MMERGE3[day]" id="mce-MMERGE3-day">
</div>
<div class="mab-field">
<label for="mce-MMERGE3-year"></label> <input type="text" pattern="[0-9]*" placeholder="YYYY" size="4" maxlength="4" name="MMERGE3[year]" id="mce-MMERGE3-year">
</div>
</div><!-- .form-dates -->
<div class="mab-field mablast">
<input type="submit" name="subscribe" id="mc-embedded-subscribe" class="mab-optin-submit" value="Submit">
</div>
<div class="clear"></div>
</form>
Then, add the following custom css code:
.magic-action-box .mab-main-action-wrap .form-dates .mab-field{ display: inline-block; margin-right: 2%; width: 25%; }
.magic-action-box .mab-main-action-wrap .form-dates .mab-field input{ box-sizing: border-box; width: 100%; }