If you want to embed a Google form is your blog.
Go to the entry. Create a text introducing the form.
Then Click on HTML next to COMPOSE
In Google forms, when you have finished your form, go to SEND FORM and click on the < > symbol at the end of the choices of how to save it.
Copy the text in the EMBED HTML text. Pay attention to the width and height. Go back to Blogger
Back to Blogger, paste (Control +V) what you have copied at the very bottom on the HTML window of your post . Click back to COMPOSE to see what it looks like. If it is too big or to small, you can go back to the Google form and adjust the width and height, copy the embedded code and come back, delete the form, click back into HTML and copy the new one.