update install command in the README

README.md

@@ -2,9 +2,12 @@
 
 ## Installation
 ```bash
-make install
+make BIN=$HOME/.local/bin VENV=$HOME/.local/share/venvs/gplt install venv
 ```
 
+> :bulb: **Note**  
+> values of `BIN` and `VENV` above are the default and can be omitted
+
 ## Usage
 > :bulb: **Note**  
 > [Nushell](https://www.nushell.sh/) has been used as the shell for the examples.