@Alex B ,
Thanks for posting the question on Microsoft Q&A.
Azure Machine Learning service is yet to be migrated to Q&A. Please post your question directly on the MSDN forum for the service (Azure Machine Learning forum)
We are actively working to onboard all services. We will make a public announcement once complete.
Thank you for your patience as we evolve the Q&A platform.
Kindly re-post the question on the ML forum on MSDN with more details on your scenario and any error you may have seen with your first experiment.
Having mentioned that, I see a good document 'Auto-train a time-series forecast model' which describes on how to prepare the feature data for forecasting. Hope that helps!
You may wish to see the article: Microsoft Q&A - Frequently Asked Questions