Change margin width

Hi Nobita-

Could you please tell me how I can change the left and right margin widths on my main pages (https://alteregovoices.com), and also on my main blog page (https://alteregovoices.com/blog), as well as individual blog pages (https://alteregovoices.com/british-female-voice-over/using-weibo-to-promote-your-voice-over-business) – thanks!!

Cromerty