insecure site reports from facebook help!

Hi guys,

can you help please.

I've been setting up some facebook ads to point to blog pages on my multisite site. Here's the url: http://swinton.yournextsteps.online/kpis-that-work/
Is it to do with the http versus https ? I'm sorry this is a big but seamingly vital gap in my knowledge!

What do I need to do to resolve this as it's mission critical!

Thanks so much