Change Sidebar Width?

Hi,

https://www.beatroutefoundation.co.uk

Could someone help me change my sidebar width in every page other than ‘HOME’? I am using pureVISION theme and its not in the options…

I understand I have to change the CSS file via edit CSS (id rather do it this way)… do I just put the change in there and it automatically updates the CSS file??

Or would i need to access via FTP – in which case is it found in the original themes folder?

Thanks in advance for your time and answers!