<fieldset>
    <legend>Sign in</legend>

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

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

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

</fieldset>

Output