Dimension Values can be sourced in two fundamentally different ways:

1. An Administrator can specify the allowed Dimension Values in advance, either by entering them manually or by fetching them from other source. If your Metric and Report data include any Dimension Values that are not listed in the Dimension Editor, they will be ignored.

• For manually-maintained Dimensions with a limited number of Dimension Values, the easiest way is to Add Dimension Values Manually
• If Dimension Values are maintained in a source system, consider automated data collection and check Create a Dimension with Automatically Populated Values
• If there is a large number of manually-maintained Dimension Values,  Upload Dimension Values from a CSV File
• If there is a Dataset containing Dimension Values, use Create a Dimension with Values Sourced from a Dataset View

2.  It is also possible to read Dimension Values from "Metric and Report Data" as it is collected. If your Metric and Report data include any Dimension Values that are not already listed in the Dimension Editor, they will be added to the list. You do not need to specify a Metric or Report – Metric Insights will collect Dimension Values from all Metrics and Reports when they are updated. For more details check the Collecting Dimension Values from Metric and Report Data article.