The Form block lets you add a form to your post or page.
The new WordPress Block Editor will be available to you as soon as WordPress 5.0 is released. If you’d like to try the editor today, you can install the Gutenberg plugin on your site. Once you’ve done so you’ll have access to all Jetpack blocks.
Requirements
To use the Form block, Jetpack’s Contact Form module must be enabled. This should be enabled by default, but if it’s not, you can enable it as described here.
Adding the Form Block
You can add the Form Block to any post or page, by selecting it from the Jetpack section of the block picker:

See our Jetpack Blocks page for more information on adding Jetpack blocks.
When you first add the Form block, you will be prompted to specify where email notifications will be sent when the form is filled out. You can enter an email address (or multiple comma-separated addresses), and a subject line. If you leave them blank, the notifications will be sent to the author of the post or page, and the subject line will be the post/page title.

Click Add Form, and a default form will be added, containing Name, Email, Website, and Message fields, and a Submit button. This can be used as is, as a basic contact form, or you can customize the form to suit your needs.

Customizing Your Form
The Form block is a special kind of block that contains other blocks. Each form field is itself a block within the main Form block. These internal form field blocks can be customized and rearranged within the Form block.
To add a form field to the end of your form, hover over the Form block and click the Add Block button that appears below the last field.

Alternatively, to add a field above an existing field, click the Add block button at the top of an existing field.

The form fields you can choose from are Name, Email, Website, Multi-line text, Text, Date Picker, Telephone, Checkbox, Checkbox group, Radio, and Select.

Note that these blocks can only be added within a Form block.
Within each field block, you can edit the field label(s) and choose whether the field is required or not.
To rearrange the blocks within your Form block, hover over the block you want to move, then use the up/down arrows to move it up/down one position, or drag it to the desired location using the dragger between the two arrows.
You can also add other non-form blocks within your Form block, if you need to include some text or an image for example.
To customize the Submit button, select the outer Form block and use the Button Settings in the sidebar to edit the Submit button label.
If you forgot to enter the email address and subject line for form submission notifications when adding the Form block, or you need to update them, select the Form block and edit the Email Feedback settings in the sidebar.
Troubleshooting
If you’re having any trouble with the Form block, please contact support for help.