I recommend that you read the Bootstrap grid system if you are going to bootstrap.
To align your button below (I assumed it was below you wanted, based on the snippet you gave), I simply added the class form-control
to the button, and put it inside a div with class col-md-12
.
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script><scriptsrc="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"/>
<div class="container">
<h2>Button Tags</h2>
<form class="form-inline">
<div class="form-group">
<div class="form-group">
<div class="input-group">
<span class="input-group-addon"><label for="exampleInputName2">Name</label></span>
<input type="text" class="form-control" id="exampleInputName2" placeholder="Jane Doe">
<span class="input-group-addon">
<label for="exampleInputEmail2">Email</label>
</span>
<input type="email" class="form-control" id="exampleInputEmail2" placeholder="[email protected]">
<span class="input-group-btn">
<button class="btn btn-default" type="button">Send invitation</button>
</span>
</div>
</div>
</div>
</form>
</div>