Centering content horizontally will depend largely on the content. Many elements are designed to fill the containing column and so will be naturally centered on the page, others naturally follow the normal text flow, like the Checklist and Toggles elements, and yet others have an alignment option for you to center the element or the content in the containing column. This includes Elements such as Alert, Image, Button, People, Title, Video, Vimeo, & YouTube. And for text content, you can use the alignment options in the visual or inline editor.
For that rare situation where there are no builder or element options to align the content as you wish, you can always use custom CSS. It’s impossible to cover every situation here, but here are a few common exampes of CSS to center content.
There are also many tutorials on the web for learning how to center things with CSS. A few places to start are: