How do I import data from Excel into a new Creator app?

Hello, I recently created a new application in Creator. I would now like to upload data from Excel tables into the database. I cannot figure out how to do this. The only information I found in help is that you can upload a spreadsheet to start creation of a new app, and I did see a post from someone else about emailing data for upload. Is it possible to upload to an existing app? If so, can you provide me with instructions? I have multiple forms/tables in this application.

Thanks very much!