This is in the help:

To enable FastSerialization you have to set the static property SerializationHelper.Optimization to one of the values of the enum type SerializationOptimization, which is either None (default, use normal BinaryFormatter serialization) or Fast.

I'm sorry if this is a dumb question but where do I set this property and how?

It's a static property so you should just be able to set

SerializationHelper.Optimization = SerializationOptimization.xxx 

anywhere in your code, and the set value will be used from then on.

Matt