Assumes you have jQuery, jQueryUI and Bootstrap 3.x already on your page.

Link the gridmanager JS and CSS files:

<link href="dist/css/jquery.gridmanager.css" rel="stylesheet">  
<script src="dist/js/jquery.gridmanager.min.js"></script> 

Create a <div> element which gridmanager will attach to:

<div id="mycanvas"></div>

If you have HTML which needs to be loaded into the editor, simply include it between the <div> tags:

<div id="mycanvas">
    <div class="row">
        <div class="col-md-6"><p>Content</p></div>
        <div class="col-md-6"><p>Content</p></div>
    </div>
</div>

Now tie in the id or class into gridmanger: you can do this two ways:

Simple implementation

<script> 
    $(document).ready(function(){
        $("#mycanvas").gridmanager();
    });
</script> 

Extended implementation

for when you want to use internal gridmanager functions:

<script>
    $(document).ready(function(){ 
        var gm = jQuery("#mycanvas").gridmanager().data('gridmanager');

        $(".myexternalcontrol").on("click", function(e){
            // Example use of internal gridmanager function:
            gm.appendHTMLSelectedCols('<p>my content to append to all my selected cols</p>');
        });
    });
</script>