How can I manually Customize the theme of running website

I am here looking for how can I manually edit the theme of my website, Currently I am running website I want to edit the theme of running site manually how can I do this I am little bit confused about the site structure and data Check my website

Hi there

Sorry, but this question is not concerned to our products, I will share results from a google search:

If you have any particular question related to our products feel free to ask them