<div>
  <label for="username">Username:</label>
  <input type="text" id="username" name="username" />
</div>

<div>
  <label for="pass">Password (8 characters minimum):</label>
  <input type="password" id="pass" name="password" minlength="8" required />
</div>

<input type="submit" value="Sign in" />

label {
  display: block;
}

input[type='submit'],
label {
  margin-top: 1rem;
}