Enhance README with example

Signed-off-by: Paul A. Clarke <[email protected]>

Author: ThinkOpenly

README.md

@@ -2,12 +2,42 @@
 
 A tool to extract information from the sail-riscv spec.
 
-## Usage
+## Build
 
 ```
 make
 ```
-then run
+This will build a `riscv_decode.cmxs` for use as a `sail` plugin.
+Example use below.
+
+## Usage
+
+In general:
 ```
 sail -plugin riscv_decode.cmxs -riscv_decode <files>
 ```
+
+A specific example follows. To ensure the various RISC-V Sail files are
+all included and in the correct order, leverage the `sail-riscv/Makefile`:
+
+1. Clone the sail-riscv repository:
+   ```
+   $ git clone https://github.com/riscv/sail-riscv.git
+   ```
+
+1. Add a `decode` target to the `Makefile`, providing the path to the plugin
+   built above:
+   ```
+   @@ -178,6 +178,10 @@ endif
+     
+    .PHONY:
+     
+    +decode: $(SAIL_SRCS) model/main.sail Makefile
+    +       sail -dno_cast -no_warn -plugin $(replace with path to)/riscvdecode/riscv_decode.cmxs -riscv_decode $(SAIL_SRCS)
+    +
+   ```
+
+1. Run it:
+   ```
+   $ make decode
+   ```