Hey there. Unfortunately, it looks like there isn't currently a way to embed Cowbird in WordPress.
A previous post attempted to embed Cowbird via iframes, and the staff answer from csonnek was this:
On WordPress.com, there are certain types of code that are not allowed to be used in posts or pages - including iframe code - due to security concerns. Here's more information on the types of code allowed on WordPress.com:
I hope that clarifies things! Let me know if you have any questions.