Wix has a rather strange blogging system that consists of "blocks". You cannot add any HTML code directly but rather use the appropriate block to do so. 

So, to use LinkDeli, you need to create an HTML block first:

and then put the code when editing it (NOT on the gray area below)

Back on your LinkDeli dashboard, just pick the code:

And paste it on the HTML box. Clicking update will produce the result below which you will see, it is a little squished! Don't worry!

Just use the spacer icons and adjust the height so that the scrollbar on the right disappears. If the number is more than the slider allows, just enter it by hand!

Publish, and you're all set!