To get data into your shinyapps.io account, the most common way is to deploy it as part of your application using the Publish button or the deployApp() call at the console. Please see the guide for more information.
The application bundle size that can be uploaded is limited to 1 GB for the Free and Starter plans, and up to 5 GB for the Basic, Standard and Professional plans. For the latter plans, note that the rsconnect package has a default bundle size limit of 1 GB, independent of your shinyapps.io plan limit. If you plan to deploy application bundles larger than 1 GB in size, you can override the rsconnect default by setting this option first: options(rsconnect.max.bundle.size=...) where the value is in bytes. Do not set the maximum size larger than the limit for your shinyapps.io plan, or application deployments will fail.
If you are working with larger datasets or would like the data to persist, we have guidance here: https://shiny.posit.co/r/articles/build/persistent-data-storage/