Go to the same page where you placed the widget that you want to add a code to it. Then paste the code you received from us, and it creates a small html container, then you can move the container to a side and pin it so when you preview/publish it wont get over your content.
you can also go from the top menu to Object > Insert HTML... and it opens a page where you can insert the code. Copy and paste the code you received from us where it says: insert your HTML here...
After you paste and click ok it gives you the exact same container.
- Pinning: to Pin the generated HTML container, select the container (which looks like an empty box with checker board pattern, then use the pinning option to pin it at the top-right side. Then move the container outside of the design area, on the top-right side. the idea is to pin it outside of the working area so it will not block the other objects. Please take a look at the screenshot.