Hover your mouse above or below an existing web part and you'll see a line with a circled +, like this:
Plus sign for adding web parts to a page
Click + to see a list of web parts to choose from. Click the Microsoft Forms web part.
Add to page button with Microsoft Forms web part selected.
Add and publish a page
If you don't already have a page with web parts, follow these steps to prepare one.
Go to the site where you want to add a page.
Go to the home page of the site.
Select + New, and then select Page.
New Page
Alternately, you can go to an existing page, select + New, and select Start from a blank page. Or, you can choose Copy of this page to create a new page that has the same web parts and content as the existing page.
Choose a page template to start with.
Template gallery
Add a page name in the title area. A page name is required to save the page. See the Customize the title area.
Add web parts
Hover your mouse below the title area and you'll see a line with a circled +, like this:
Plus sign for adding web parts to a page
Click + to add content like text, documents, video and more. To learn more about how to find and use web parts, see Using web parts.
Add to page button
You can also add sections and columns to a page. To learn more, see Add sections or columns on a page.
When you're done editing, you can click Save as draft to save your changes and close edit mode. Your audience won't see the page until you publish it. Only people with edit permissions on your site will be able to see it.
When you are ready for your audience to see the page, click Publish.