Hi,
If you are not familiar with the PLC Database File Editor I would suggest you read up on how to use it first, then you can create modules.
Firstly you would need to create custom terminal blocks.
If you go to the PLC Database File Editor and click the settings button you will get a list of existing Terminal blocks, these are what your existing PLC modules are built from. You can create your own blocks that can then be used to build your custom PLC module.
Next you would need to create your PLC module using the Terminal blocks you have just created, info on how to do this can be found in the help.
If you get stuck on the specifics let us know.