Asp.Net MVC3: Add new Entity to model

We have a .Net ASP MVC3 project based on the Entity framework and using Mysql as database. The use of mysql gives some problems when adding new entities to the model. Problem is to achieve a correct edmx as automatic generation fails. So the task is simply to add a new Entity/Model class to the project and describe the correct procedure for doing this in the future. Source code available upon request