Redmine

hello every buddy:

i try to create a new plugin. but it is to hard for me created I modificate the core code in the redmine source, but when i try to create i don't understand the plugin how to. i only modificate the issue.rb the part of one array where it says SAFE ATRIBUTES and the class issue_relation_helper i create a new method in there and in the model issue_relation i modificate the array of types can any buddy help me how create this modifications please

thanks