Contact form in a default.md

Hi, I have created a page form.md with a contact form. I don't understand how insert this form in a default.md or others pages... I have read to include the form in a twig but in the guide there's no written how...

Maybe the following documentation chapters may help:

• Example: Contact Form
• How to: Forms in modular pages.
  Take note of the following:

  !!!In Form v2.0, you can now define the form directly in the modular sub-page just like any other form.