How can I embed a form in my google sites

I have been trying to embed a simple newsletter signup form on my google sites page for over a year. Unsuccessfully. Tried mailchimp, didn't work. Was encouraged to see Jotform had detailed instructions on how to do this, but it doesn't work. I've tried variations, embed gadget on my google site, I've tried iframe, I've tried add gadget my URL. I either get a blank white box or it says its invalid. 

Please tell me this is not hopeless and I'll never be able to get a form on my site emersondoering.com

Help!

Thanks,

Sharon