[Editor Mike]

My forum is here:

https://www.thewargameswebsite.com/forums/

How do I make it wider?
I need to keep the sidebars, so if making the forum wider makes the whole site wider that is fine.

TIA

[Robin W]

The width is governed by a div with the class rt-container, but it is not clear what craetes that.

Try this in the custom css part of your theme

.rt-container {
	width: 1500px !important;
}