README fix

other/protobuf/README.md

@@ -9,3 +9,14 @@
 - `protobuf_ast.py` - Dataclass definitions for a Protobuf AST
 - `protobuf_ast_construction.py` - Define helper functions that build AST nodes
 - `protobuf_to_ifex.py` - AST Model-to-model transformation Protobuf->IFEX
+
+## How to run
+
+For simple conversions or tests, the protobuf_to_ifex.py has a main method and can be run as a script directly. It will print out the 
+result as IFEX Core IDL in YAML text:
+
+```
+python protobuf_to_ifex.py <input.proto>
+```
+
+For developing on top of this module, for example in a direct translation to other format without the IFEX text format as an intermediiate:  Import and use the function `proto_ast_from_input(protofile)` followed by `protobuf_to_ifex(proto_ast)` on that result.  The latter returns an IFEX AST that can be further processed.