Hi jkeuning,
Thank you for reaching out to us on Microsoft Q&A forum.
One login into the Power BI service. Left side you can find the create option under the create we have multiple data sources like Excel, CSV, if you want to connect any cloud data sources in same page please scroll down.
Once you selected the data source you can start build the report.
Note: Every month Microsoft will update preview features in both Power BI Desktop and Power BI Service.
If you are still facing any issue, please let us know in the comments. We are glad to help you.
If the information is helpful, please Accept Answer so that it would be helpful to community members.
Thank you.