How do I make Web Page (iframe) wider

Hi , very new to Home Assistant (which is fantastic . thank you to all involved) started to create dashboards using love lace , but how do I make a web page (iframe) wider? I can see the aspect ratio which doesn’t really help and only makes my pages longer.

Ive seen some suggestions re addon such as card-mod to change the css but I’m not to comfortable with that just yet as not used css before so not sure I understand how to apply in this case.

All help is appreciated, thank you … Andy