For both of these you will need to use the Visual Builder.
For the Contact Form:
Open it and click on Add New Field.
Set a title to it and select the Checkboxes type from Field Options. You'll see a checkbox added instantly to your form:
3. In the Options field write your text with the link to the website's policies:
Here's a live demo of the above:
For the Email Optin:
After you select the Service Provider (I've did this example with MailChimp) go to Email Optin Settings -> Fields and click on Add New Custom Field:
2. Add the custom field which is created in the Service Provider:
Further customize that field and make it Required if needed and add links too:
Here's a live demo of the above:
