Updating the theme and visual composer

Hi, I have a question regarding the update to the latest theme. I am using the child theme supplier with the download so am hoping the update will be quite straight forward.

Could someone explain to me simply how I go about updating the theme and removing the old theme files? I am not a web developer so my knowledge is limited to what I have picked up working on wordpress sites.

I have a site live that uses the theme and I’m experiencing issues with the backend visual composer where text boxes are no longer updatable on new pages – it must be that the plugin needs updating but there’s no option in the backend to simply update this, so am a bit stuck.

Any help and advice will be greatly appreciated, in layman terms too please!

Thanks

Caroline