<form>
<div class="input-group mb-3">
<div class="input-group-prepend">
<span class="input-group-text">@</span>
</div>
<input type="text" class="form-control" placeholder="Username">
</div>
<div class="input-group mb-3">
<input type="text" class="form-control" placeholder="Your Email">
<div class="input-group-append">
<span class="input-group-text">@
example.com</span>
</div>
</div>
</form>