Hi there,
If you set your Logo and Navigation layout to Stacked, the logo and the menu will be automatically centered without any custom CSS just like the demo here:
http://demo.theme.co/integrity-9/
If your layout is set to Inline the default placement of the logo will be on the left and the menu on the right. If you want to push them closer together to the center, it would involve some custom CSS with some media queries so that you can set the maximum with of the container depending on the screen width like this:
@media (min-width: 980px ) {
.x-navbar-inner .x-container.max {
max-width: 900px;
}
}
The code above should help you get started. Kindly remove the previous code you have added then adjust the value of the max-width in the code.
Here are some reference links related to the suggestions above:
Please note that since this is modifying the default display of the theme, it requires some customization which goes beyond the scope of our support. If you are not comfortable making further changes and if you require more customization on your site, it would be best to get in touch with a developer.
Hope this helps you get started.