HELP! How do I configure Simulink to recognize the target DSP?

I'm trying to implement the LED exercise at
http://dsptute.blogspot.com on a TMS320C6713GDP DSK kit.

The Simulink drawing (led.mdl) is straightforward enough just a
constant 6 input to a C6713 DSK LED. I've used the C6713 diagnostic
utility to confirm that the DSK kit is properly connected to the
computer and the power source.

But I can't for the life of me figure out how to properly configure
everything. I go to the Simulation menu in the led.mdl window and
change from Normal to External. I go to the Simulation menu in
led.mdl, select Configuration Parameters, and go to Real-Time
Workshop. I change the system target file to ti_c6000.tlc . I go
to the Solver part of the Configuration Parameters window and change
the fixed step size from auto to .2.

The Build button I'm supposed to get does not exist - a Generate
Code button is there instead. So I click on the Generate Code
button and get the following error message in the Simulink window:

"Error building Real-Time Workshop target for block diagram 'led'.
MATLAB error message:
Error using ==> callMakeHook.p>callMakeHook
The call to ti_c6000_make_rtw_hook, during the before_tlc hook
generated the following error:
Error using ==> checkModelAndSystem_DSPtarget
Error using ==> getTargetInfo
The model must have a C6000 Target Preferences block.

The build process will terminate as a result."

I get the following error message in the MATLAB window:
### Generating code into build directory:
. . . dskprojects\simulink1\led_c6000_rtw security reasons>
Error executing m-file getIRInfo_C6000DSP ...
Error using ==> getTargetInfo
The model must have a C6000 Target Preferences block.

Using the Incremental Build command in led.mdl yields the same error
messages.

Using the "Connect To Target" command under the Simulation menu in
led.mdl yields the following Simulink error:
Current Real-Time Workshop target for model 'led' is either not
configured for or does not support external mode. In Interface page
of the Real-Time Workshop page of Configuration Parameters dialog,
select Interface option to be "External Mode" to enable external
mode for targets that support it.

and the same MATLAB window error message I was getting before.

This is so FRUSTRATING! So close, and yet so far!