To edit and format equations and mathematical formulas in OneNote, you should follow the steps below:

1. Type out your equation or mathematical formula in the OneNote text box.
2. Highlight the equation and select the Equation options from the Ink Recognition menu.
3. Choose Edit Using Math Assistant to open the Equation Editor window.
4. Use the options in the Equation Editor window to format your equation as desired.
5. To save your changes, select the Done button.

This process should help you to easily edit and format equations and mathematical formulas in OneNote.