Be sure you save your actual tax file to a flash drive before you delete anything. Search for "*.tax20XX" (substitute the two-digit year for XX). You'll need it next year.
Using a Windows computer, you should be able to uninstall TurboTax Desktop from the Start Menu >> All Apps. Find TurboTax 20XX, right click and choose "Uninstall."
To confirm all files have been removed, go to C:\Program Files\TurboTax and looks for a folder for Individual 20XX. If you find that folder, delete it.
Your actual tax data is in a file, like a word processor or spreadsheet file. It is usually located in the documents folder and will have a name like "yourname 2025.tax2025". You can delete this file, but you should keep a copy, and you should also generate a PDF and save that for later, before you delete the main file.
If you also want to remove the program from the computer (uninstall) you may need your friend to log in with their administrator password.