Theme or template files are located in /templates/wtkdefault/ folder. Html and css files can be modified to change the look and feel of the website.
It is recommended to make a copy of ‘wtkdefault’ folder in the ‘templates’ folder and do the modifications. You can switch the website to use the new template from Admin > Configs page, Site Template field.
Individual page theme/template is located in /tmpl/ folder. These files can be modified, but modifying these files will prevent you from updating the website to higher version when new version updates are released. You must manually merge the code changes.