You are talking about post_meta data – information stored about a page or post which is not part of the standard fields – title, content, image etc.
WP has support for post_meta built-in, but you might not be able to see it – perhaps the “custom fields” panel is hidden or you have create a new custom post type and not added support for custom fields.
Try the “screen options” in the top right, or check the features supported by the post type – if missing, you can add additional support either via add_post_type_support or updating the code used to register the post_type.
Custom field ( post_meta ) data can be retrieved using the get_post_meta function – the same data can be loaded once and re-used several times within the same template.