How can I update our form?

I want to change my form please let me know how can I change that form?

If you mean editing the form, you need to login to the account where it was created. And from there, you can make changes or edits. 

Changes made to the form will automatically reflect on your website.

In case your referring to changing the embedded form on that website with another form, you need to edit that webpage and embed a new form. Please refer to this guide on Embedding-a-Form-to-a-Web-Page.