RE: Release 2020 Wave 1 - New Functionality for Marketing Forms integrating in third party CMS
Hi Jennifer,
Currently we don't document guide of integration with 3rd party platform.
There are few steps to work with Form capture:
1. Create a Marketing website record, copy automatically generated code from both JavaScript code field and Form capture code field to your external web page.

Purposes of those two fields:
JavaScript code:
This is the code that you must place on each webpage that you want to track as part of the current website. It is read-only. Copy the code from here and paste it onto each webpage (or CMS template) as needed.
Form capture code:
This is the code that you must place on each external webpage that includes an externally designed form that you'd like to use to submit data back to Dynamics 365 Marketing. Copy the code from here and paste it onto each webpage (or CMS template) as needed. More information: Use form capture to integrate a form created externally.
2. Create a new marketing form record by click "New form capture" button, then add the URL of your external website to Form URL field

If your form is static HTML form, scanner will find input fields quickly

Map fields from the source form to Dynamics 365 form fields, then go live the record.

Could you share me what problems you have encountered with form capture?
If your form is built by Wordpress plugin such as Contact 7 and the form fields couldn't detected, please copy HTML code of the built form to set the form as static.
I found that the doc tutorial about form capture has changed(the doc was updated on 5/11), did your encounter any trouble with new tutorial?
If so, I will upgrade my instance to latest version and do test for you.
Regards,
Clofly