I bought an open diff 2 way for my factory VLSD car
 

Got a great deal on a Tomei 2way. It is the version made for the open diff base models.

My car is a factory VLSD 6MT.

What do I need to make sure they work together? Will I have any issues?

From what I remember it will not work in cars that came with vlsd.

double check which stub axles the Tomei lsd needs. Open diff stub axles are different lengths than VLSD stub axles.

When I bought an OS Giken LSD for my 6spd manual Z, which had the viscous LSD from factory, I also had to buy an additional axle for the left side of the car, that was slightly shorter than the one that I had in my car. I guess it's something similar for Tomei - just check what exactly you need. Replacing the axle is a non-job, as you need to remove axles from the diff housing anyway when you're installing the LSD, so you'll just replace the axle with the other one.
I suggest you shoot an e-mail to the Tomei distributer and ask them what do you need in addition to the LSD, to make it work with the factory VLSD 6spd car.