Since you got these RAM modules from OWC, I would suggest that you contact them directly and have them assist you with this. I would think the first thing would be to double-check that these modules are the correct ones for your Mac. Your Mac also should have “built-in” instructions on how to properly add the additional memory and to what slots when using modules of different capacities.
FWIW, I have been an OWC customer for years and have only had the best experience with their products and their support staff for things just like this.