Thanks for posting in the Lucidchart Community! Unfortunately, Lucidchart does not currently offer a desktop version of the software. In the past, Lucidchart has offered a browser extension for easy access to the application, but has not offered a desktop application. Apologies for the confusion! Files downloaded from Lucidchart are generally not able to be re-uploaded, as all files are stored in their most recently saved state in your Lucidchart account. Unless the files were deleted after download, they should still be available in your Lucidchart account. To access these files, you'll need to log in to your account at Lucidchart.com. If you need any help logging in, let me know!
Once logged in, you should be able to access all of your Lucidchart files. Please try this, and let me know if you encounter any issues! If so, our support team is happy to help.