如何更改机器生成的代码

perhaps its a stupid question but I have created an interface by using the Design mode in Netbeans but now i need to make some basic changes to it, specifically i have created a part of the interface which works, in design mode but now i need to create some checkboxes array therefore i need to create them manually the issue is how can i connect these two? I mean how can i add the manually created code to the rest of the code? The automatic code wont allow me to make changes and add code to the variable declarations.I have to add codes to the following part for exampleperhaps its a stupid question but I have create