<fieldset>
    <legend>Choose your monster's features:</legend>

    <div>
      <input type="checkbox" id="scales" name="scales" checked>
      <label for="scales">Scales</label>
    </div>

    <div>
      <input type="checkbox" id="horns" name="horns">
      <label for="horns">Horns</label>
    </div>
</fieldset>

p,
label {
    font: 1rem 'Fira Sans', sans-serif;
}

input {
    margin: .4rem;
}