Embed Gymcatch booking system using code blocks

Site URL: https://danceflooractivist.co.uk/book-a-class

HELP! I'm trying to embed Gymcatch booking system onto a site and nothing seems to be working. I have basic coding knowledge so have troubleshooted and searched and searched but there's nothing out there. 

Here's the code they propose to input:

<!‐‐ Insert the gymcatch-embedded tag in your html ‐‐> <!‐‐ You will need a unique key from Gymcatch ‐‐>

<gymcatch-embedded key="GYMCATCH_EMBEDDED_API_KEY"></gymcatch-embedded> <!‐‐ Load the Embedded app javascript ‐‐> <script src="https://app.gymcatch.com/js/bootstrap.js"></script>

I've obviously edited myself to include the API key needed. I've tried inputting the whole thing into HTML as well as javascript but I'm stumped.

Here is the companies own tutorial which hasn't really helped. Hoping someone here can-

https://gymcatch.com/business/installing-gymcatch-on-your-website/#squarespace

Which position did you insert code in above link? I don't see Code Block.

Sorry what do you mean by position?