JSFiddle - React, Tailwind, and code Playground

HTML

<div class="index-content-right">
                    <h2 class="index-content-title">Записаться</h2>
                    <p>Укажите желаемую дату и время и мы свями свяжемся для подтверждения брони</p>
                    <form class="oppointment-form" action="http://echo.html-academy.ru" method="post">
                        <input type="text" name="date" value="" placeholder="Дата">
                        <input type="text" name="time" value="" placeholder="Время">
                        <input type="text" name="name" value="" placeholder="Ваше имя">
                        <input type="tel" name="phone" value="" placeholder="Телефон">
                        <button class="btn submit" type="submit">Отправить</button>
                    </form>
                </div>

CSS

.index-content-right {
    width: 300px;
    }
    
    .btn {
    display: inline-block;
    background: #000000;
    color: #f4f1ee;
    text-transform: uppercase;
    border: none;
    font-size: 14px;
    line-height: 24px;
    text-decoration: none;
    letter-spacing: 0;
    cursor: pointer;
    padding: 10px 33px;
    vertical-align: top;
    text-align: center;
    margin-right: 16px;
    }
    
    .index-content-title {
    font-size: 30px;
    line-height: 42px;
    margin: 0;
    margin-bottom: 25px;
}

.oppointment-form {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
}

.oppointment-form input {
    background: #f9f6f3;
    border: 2px solid black;
    font: inherit;
    text-transform: uppercase;
    color: #000000;
    padding: 7px 15px;
    margin-bottom: 20px;
    width: 106px;
}


.submit {
    width: 100%;
    font: inherit;
}