The TurboTax online web-based editions and the TurboTax desktop editions installed on personal computer are totally separate programs with different price points. So you cannot switch from the online Premium edition to the desktop Premier edition at no charge.
Go to this TurboTax website for the desktop editions - https://turbotax.intuit.com/personal-taxes/cd-download/
If for some reason you decide to use the desktop editions you can transfer the online tax data file to the desktop edition. See this TurboTax support FAQ - https://ttlc.intuit.com/turbotax-support/en-us/help-article/import-export-data-files/save-turbotax-o...
