place inside the nbextensions folder enable via:
$> jupyter nbextension enable default_cells/main --sys-prefix
Add default cells to each new notebook. You have to modify this line in the main.js file to change your default cell. For example
Jupyter.notebook.insert_cell_above('code', 0).set_text("import numpy as np/nimportpandas as pd")
You can also add another default cell by creating a new line just below :
Jupyter.notebook.insert_cell_above('code', 1).set_text("from sklearn.meatrics import mean_squared_error")
**Don't forget to increment 1 if you want more than one extra cell. **
Look in /usr/share/jupyter