After you have verified that the .mnf file contains accurate information, you are ready to run an Adams simulation with a flexible component. Import the .mnf file into your Adams model and attach it to the rigid bodies using joints. To keep any numerical imbalance between inertia and external loads small, make sure you simulate your Adams model with high accuracy.
For general information about the Adams program and how to import flexible bodies, refer to the Adams manuals (provided MSC Software), especially the documentation provided for the Adams/Flex product.