Update Ortac/QCheck-STM README

plugins/qcheck-stm/README.md

@@ -60,10 +60,18 @@ indicate:
 - how to generate an initial value of that type, for instance
   `make 16 'a'`.
 
-Using those example values, you can run
+You can do so with the following `lib_conf.ml` file:
+
+```ocaml
+open Lib
+type sut = char t
+let init_sut = make 16 'a'
+```
+
+You can then run:
 
 ```shell
-$ ortac qcheck-stm lib.mli "make 16 'a'" "char t"
+$ ortac qcheck-stm lib.mli lib_conf.ml
 ```
 
 to generate the corresponding QCheck-STM program. The [QCheck-STM
@@ -75,7 +83,7 @@ one that is generated by the plugin.
 You can then save this module into a file:
 
 ```shell
-$ ortac qcheck-stm lib.mli "make 16 'a'" "char t" > main.ml
+$ ortac qcheck-stm lib.mli lib_conf.ml -o main.ml
 ```
 
 and compile this into an executable using: