If you mean this one why not post the link?
at a glance this device GENERATES PWM and the function of the arduino would be to tell it what to do over the serial interface. You would need to handle that yourself unless someone is aware of code or a library to do it as its not rs232 & ff standard.
I think we have been trying to find a way for an arduino-ish device to PRODUCE that pwm which seems not to be your intention.
The TLC5940 has a flexible serial interface, which can be connected to microcontrollers or digital signal processors in various ways. Only 3 pins are needed to input data into the device. The rising edge of SCLK signal shifts the data from the SIN pin to the internal register. After all data is clocked in, a high-level pulse of XLAT signal latches the serial data to the internal registers. The internal registers are level-triggered latches of XLAT signal. All data are clocked in with the MSB first. The length of serial data is 96 bit or 192 bit, depending on the programming mode.