I understand nothing ... Example ConfigFile ? Where i put the Settings  ?

There is no config file. This plugin is a api for other plugins to utilize. It's supposed to allow plugins to gain access to data after they have been reloaded.
For example, a plugin that contacts a web resource every time it's loaded could cache the response in the memory cache and check the cache first next time the plugin is loaded instead of blindly contacting the api and wasting resources. 

... and how do I tell a plugin how to use your plugin?and where do I set how much memory and how long it should keep the data?

BennyThrydurps

... and how do I tell a plugin how to use your plugin?and where do I set how much memory and how long it should keep the data?

The other plugin would need to set that and add that to their config file. All cached memory is cleared when MemoryCache is unloaded.