add usage

README.md

@@ -2,5 +2,16 @@
 
 This repository is intended to include utility-functions for quantum chemistry courses.
 
+## Installation
 
+```bash
+pip install git+https://github.com/QC-Edu/QChem-utils.git
+```
 
+## Usage
+
+```python
+from qctools.hydrogen import hydrogenic_wavefunction
+
+hydrogenic_wavefunction(1, 0, 0, 1, 0, 0, 1)
+```