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Dear Dexter @dexter
In the Customize section you have the option to 'center' however if this is not a solution for you there is:
margin: auto - left and right
or using Calc: to keep things centre
or if applicable align-items, but this requires 'flex'
There are a few ways - if you could post a link to your website with the menu in question and then we can see what suits! :)