How to make the mailchimp form in 1 line

Hello Sir,
I have integrated mailchimp in my website.
I want to change the css of the form,I tried but I could not.
Please help me write the css.
I want the fields in 1 line like
firstname texbox lastname textbox email textbox submit. This should be in 1 line.
Here is the output http://aureusart.com
Please help me.

Thanks