It is impossible to upload a program inside any codesys PLC, as the program is fully compiled for the processor in the PLC.
If you do not have any source code it will be very very difficult.
There is NO decompiler for version 2.3 available (would love to have it though).
downloading to a PLC is easier, by cable or via internet, however you must have your communications setup correctly, as codesys supports many PLC types, you will have to be more specific.