A few important points in doing this:
1. You'll need to configure the Call Library Function (CLF) to pass the array using "Array Data Pointer" format.
2. I'm assuming that the DLL expects that the memory at data has been allocated by the caller. If that's the case, you should create a constant array of doubles on the LV block diagram, whose size is sufficient that the DLL will not write past the end of the array, and pass that array into the left hand side of the CLF. Otherwise you'll crash.
Steven H.