Module Builder V3.5.1 helps in creating new modules and uploading
them into SugarCRM. This version supports SugarCRM 4.2.0d. You can
download the zip file from here.

Once you have downloaded the zip file then you can upload this in
SugarCRM 4.2.0d through Admin>Module Loader. You would also
require the Module Builder Simple Template to make Module Builder work.
Download the zip file from here. Now upload the zip file in SugarCRM 4.2.0d. Now you can see the Module Builder in the Sugar tabs.

Once you have installed both the zip files now you can start
creating new modules with the help of Module Builder. You may have to
follow the simple workflow to create and show the new module.

Fill all the mandatory fields and then hit the save button. Now again open the module through module builder list and build the module by hitting the build module button. Now download the new module and then finish the module building process.

Now you can upload the new module through Sugar module loader and then install the new module. After installing the module it will be visible in the Sugar tab.