Updated README.md with usage instructions

README.md

@@ -19,8 +19,15 @@ Traditional access control mechanisms in operating systems allow the same level
         - Debian: `sudo apt install zenity`
 * Build using `make`:
     + In the project directory: `make`
+    + Use `make DEBUG=1` for testing.
 * Resulting binaries should appear in the `build` directory.
 
+## Usage
+
+`icfs <FUSE arguments> [target directory]`
+
+The filesystem will be mounted over the target directory, and ask user permission every time a file in that directory is opened.
+
 ## Docs
 
 - [Initial idea and motivation](./docs/bc-thesis-idea.md)