Form not appearing

I just installed the Email subscribers plugin and have inserted the code into a widget. However, a form didn’t appear. All I got was some gibberish words in it’s place.

How do I get the form to appear? This is all I see on my site:

[widget box]Even if it ain’t pretty it’s fricken cool, best hing since sliced thebread and instant is a sliced thebread and instant is a sliced thebread and instant is a cool,st thing since sliced thebread and instant is a ven if it ain’t pretty it’s icken sliced .[/widget box]

https://www.ads-software.com/plugins/email-subscribers/