Hi Devon,
First of all, the "Guides & How-tos" is meant for, well, actual guides. If you have questions of a technical nature like the above, you can better use the Tech forum, as it is better frequented and you'll receive an answer sooner.
As for your question, I've never used the Excel upload etc. myself, so I'm not sure what went wrong. However, if you've added an attribute to an entity, the aggregate should just fetch it. If you added a new entity however, you'll need to add it to the aggregate. I'm sure that if you advance in the tutorials, it will be explained how to do that, but what you can do is open the aggregate, and drag the new table onto it.
First of all, the "Guides & How-tos" is meant for, well, actual guides. If you have questions of a technical nature like the above, you can better use the Tech forum, as it is better frequented and you'll receive an answer sooner.
As for your question, I've never used the Excel upload etc. myself, so I'm not sure what went wrong. However, if you've added an attribute to an entity, the aggregate should just fetch it. If you added a new entity however, you'll need to add it to the aggregate. I'm sure that if you advance in the tutorials, it will be explained how to do that, but what you can do is open the aggregate, and drag the new table onto it.