If your Marketo form fields do not match object fields in Salesforce, then you will want to use the map:true option within the snippet so that we can properly find and map these object names.
If your form field names are already match the SF standard object names, you may be able to skip this step. For info on that, see this article.
In this article we will cover the three steps required to implement this code:
Customize the snippet for your form
The code is exactly the same as what we have in our router embed settings within the router with one notable difference, adding "map:true"
The first string, "calendar" is your account name, and the second string "prod-testing-router" is your router name - you will want to copy this exactly when creating the API code.
Once these two components are updated, and map:true added, you will want to add this new code below your Marketo form.