You have created custom fields and need them to be visible in Segmentation and Content...

In the Marketing Extensibility app, go to Assign to Segmentation and set the field visible for the appropriate ^ Business Context and Segmentation Object.

In the Custom field and Logic app, edit the custom field and enable Segmentation Usage in UIs and Reports.

In the Segmentation Configuration app, navigate to the appropriate data sources that are used for the Segmentation Object and mark the corresponding attributes as visible

In the Custom Fields and Logic app, edit the custom field and select the appropriate Business Context and ^ Segmentation Object.