Typically, your problem specific data structures and algorithms are implemented in a Java class (or set of classes). This how to overviews the steps you should do to develop the code for your problem optimization.
The first step in solving a problem with JECoLi is to decide on how to represent a solution for the problem. Please check the Choosing a representation how to.
Next, you need to define an evaluation function. This class defines the way fitness is calculated for each problem, being of foremost importance for solving a specific problem. This is the glue between the problem and JECoLi. This subject is covered in more detail in the Creating evaluation functions how to.
The following step involves selecting a given algorithm, configuring and running it. A number of how to's for specific algorithms are available to illustrate this task.