Here is the help, how you can change the file in one task if that uses file upload:
- Edit the right task (clicking on the Edit button or simply click on the name of the task)
- Click on "Add file" on the top of the wizard
- Click on the "Drop here..." section, browse the file on your local computer
- Click on the upload button (this uploads the file)
- Click on the done button (this saves the structure)
- Click once on the next button (this saves the step)
If you used the same file headers like you previously did, you do not need to modify the Field mapping section, just click on the dashboard and hit once the run button if you want to run the task with the new data. However, if your headers are different, you will need to do the mapping again.