Widen text area in Posts section of website

Hi

I’m pretty new to all of this. Can anyone help with widening the text area in the Blog area of the following site:

https://kumbayah.com.au/?page_id=39

I’m not sure if it’s a sidebar issue or if it’s the page width, have tried editing both to no avail.

Please help!

Thanks

Justine

https://www.ads-software.com/plugins/mingle-forum/