updated readme

README.md

@@ -5,6 +5,11 @@ A command line password generator implemented in Rust
 
 `cargo build --release && ./target/release/sphinx-passwords`
 
+### Usage Options
+
+- Use `-l` or `--length` with a number to set the length of password for example: `-l 34` returns 34 characters. This option defaults to a random length between 10 and 20 if is not passed.
+- Use `-s` to mute all messages, only returns the password. This is useful to use the binary in a script or an automation tool
+
 ## Tests
 
 Tests are in tests folder, to run tests use `cargo test`