Hi
How do you connect to your data source? If you connect to some database data sources or SSAS via DirectQuery/Live connection, there is no option to configure scheduled refresh in Power BI Service. Scheduled refresh is only available for imported datasets. For more details, please review this article.
However, if you connect to your data source via import mode, you would need to install gateway and add data source under the gateway, then you are able to schedule refresh for your dataset.
Thanks,
Lydia Zhang