It is tricky to manually create an alignment from scratch using the HALGN linemode code. Generally most users would do minor editing of the HALGN code, transition length and radius adjustments.
If you have an AutoCAD alignment the process I would use is to import the AutoCAD element to an MX model as an alignment and use the alignment tool to create the HALGN code output for the alignment. You can export the model to a genio file to create the genio data for the model.
