Load your flight plan using "File -> Import". The file you select must be an FSX or FS9 .pln file. To save the flight plan in the INS format you click on "File -> Export". Then you select your destination folder and filename. When you click on "Save", several different files are created in the destination folder. If your filename is "file", these files might be created:

file.1.AWC              - A file representing an ADEU card for the first 
file.2.AWC              - The next waypoints. 
file.ADC                - A file containing DME updating positions. 
file.txt                - A description of the flight plan.

One or more AWC and ADC files are created depending on how many legs you have in your flight plan, since the INS can only have 9 waypoints at a time and you can't overwrite any active waypoints.

On the left side of the main interface you will see a list of legs. These are the legs which will be added to the exported flight plan. You can add text notes to each leg. These notes will be added to an output file. A semi-colon (;) in the note for a leg will be replaced by a line break in the output file. E.g.

Below FL140;Above FL110

is replaced by

Below FL140 
Above FL110

On the right side of the main interface you have a list of all the waypoints in the imported flight plan. Here you can decide which waypoints should be in the plan. If you wish to remove a waypoint from the flight path, simply untick its "In plan" checkbox. It will be removed from the list of legs. You can also decide which waypoints should be exported to the DME updating, ADC, file. You add/remove a waypoint by ticking/unticking the "ADC" checkbox. Please not that only VORs can be added. The checkboxes for all VORs are automatically checked when a plan is imported. Often the altitude data exported for the waypoints are incorrect. Correct altitudes improve DME updating accuracy. You can set the altitude by entering the VORs altitude in the "Altitude" column in feet. If you want the navaids frequency to be displayed in the ADC and flight plan text files, you should enter it in the "Freq" column.

In order to load the files in the INS system, you need to put the .AWC and .ADC files in your "...\Microsoft Flight Simulator X\civa\ADEU" directory. Then you can load them as described in the Concorde-X Navigation Manual.