Update the README

README.md

@@ -74,6 +74,10 @@ If you run `make`, you will generate a documentation accessible from [`doc.html`
 
 ## Usage
 
+You should first generate the serialized `.llbc` file by calling Charon from *inside*
+(similarly to cargo) the crate you want to translate. **Important:** you should call
+Charon with the `--hide-marker-traits` option: `charon --hide-marker-traits`.
+
 The Aeneas binary is in `bin`; you can run: `./bin/aeneas -backend {fstar|coq|lean|hol4} [OPTIONS] LLBC_FILE`,
 where `LLBC_FILE` is an .llbc file generated by Charon.