First things first, let's see how we would easily do that with an iFrame:
<iframe src="https://instant-scheduling.com/sch.php?kn=123456"></iframe>
So the above is going to help you add the scheduler to your webpage. Now you may want to remove the top banner (with your business name and description) since this is probably redundant on your website. Here's what you need to change to make it happen:
<iframe src="https://instant-scheduling.com/sch.php?kn=123456&nobanner=Y"></iframe>
Note the
&nobanner=Y
that we added to the link. That's all it takes :)