Modify the source code

I’m new new here.
I’m interesting in design my web by HTML.
How can I do it ? the source code is lock.

What PKP software product and version are you working with, and what specifically are you wanting to do?

I want to do visual design for the website, like fonts, colors and locate things in different places

Most of the changes involving the visual design of fonts, colors and reflowing the box model will be handled by custom CSS and the settings in Journal Setup, Step 5 “The Look”, especially 5.6 Journal Layout.
User Home → Journal Manager → Setup → 5. The Look → 5.6 Journal Layout

For customization beyond that, check out this thread: