The Collums online booking site is an iframe and is easy to embed into your own website.
If you have access to your website code and now how to insert an iframe, use the following code or a variation of it:
<iframe src="https://yourclinicname.collums.co.uk/"width="100%" height="650" title="Your Clinic Name Online Booking"></iframe>
yourclinicname = the first part of your collums url e.g. yourclinicname.calendar.collums.co.uk
You can change the size of the iframe by changing the numbers (or percentages) in quote marks after width and height in the code above.
If you don't have access to the code or need help, it should be straightforward for your web developer to do this.