Position the cursor where you want to insert a formula, click Insert-Formula, and then select the formula you want to insert. For example, we now choose "quadratic formula".

At this point, the standard form of quadratic formula has been inserted into the document and automatically switched to the formula tool. Next, you can design subscripts, radicals, etc. If there is no formula you want in the toolbar, click the Ink Formula button in the Formula Tool-Design-Structure group, and you can manually enter the required formula in the open panel.

Finally, we can save our own formula as a new formula. Of course, we can also input formulas according to other formula editors, which is also very convenient.