Revise usage section in README.md

Updated usage instructions for clarity and detail.

Author: StRigaud

README.md

@@ -15,8 +15,9 @@ To install the plugin, download and copy the `.jar` file in the `plugins` direct
 
 ## Usage
 
-From Fiji, open the image that you want to process.  
-Launch the plugin from `Plugins>Cellpose-Appose>cellpose appose`.  
-An interface will pop-up to let you choose the parameters to run Cellpose.  
-Enjoy!   
+From Fiji
+- Open the image that you want to process.  
+- Launch the plugin from `Plugins>Cellpose-Appose>cellpose appose`.  
+- Parametrise your Cellpose run through the Graphic Interface
+- Press "Ok" and Enjoy!