Login to your Jimdo account

Open your site menu, then click "Settings".
​

Select "Edit Head"

Copy the Book Now library from the head tag (see here for info) and paste it in the appropriate area. It should look like this:
​

Save your changes.

Then, go to the page you want the button to appear on.

Click "Add element" in a section where you want the button to appear.

In the "More elements and Add-ons" section, select "Widget / HTML"

Copy the Book Now configuration code from the body script and the button code and paste them together here. It should look like this:
​

Save your changes, then test your button.