To start up with a contact form at your site, you first need to register a account there. You can do it by clicking here.
Once you do it please follow the steps given below so that you will get a contact form at your site.
Step1: In dashboard click Create New Form
Step3: Type the form name and click OK.
Step4: Click continue at top right.
Step5: If you want to add an email for notification, do add it and click save down. Now click continue again.
Step6: Towards left Click 'Embed Code' below 'Form Link'.
Step8: Got to blogger => Choose the blog where you want to add => Pages => click new page=> click blank page.
Step9: Once you created a new page type a name for it, then click on HTML, besides Compose and paste the copied code there. Click publish...
Click here to see an example