C# program pass data to a 3rd application program

I have a 3rd application program and a c# program. The 3rd app program need user to browse the filename, key in same password every time user need to upload the files. The C# program is to get and save the folder source, destination path, and the password read from excel. My question is, how can i pass all the data from the c# to the 3rd app program. what method should i used? any references are very helpful. Sorry, i dont know how to xplain in the exact words. Any references are very helpful. thanks in advance!!