To create a new form go to Form Templates on the left and click the New Form Template button. Enter your form name, assign it to a group, and paste the HTML for your form in the text area. This will create version one of your form. Next you will be brought to a screen where you set form section permissions. After that you will be brought to the summary screen for that form. You must activate the form version before it is usable. You will find a link to the form itself on the Form Templates screen.
Every time you edit the HTML of this form a new version is created and has to be activated before it is available. Any data entered in a form, whether the form is in process or already archived, is always tied to the version of the form when it was created, never a newer version. From the Form Templates screen you can use the "View" button so see the version history of the form, preview any forms in any lifecycle state, and activate old versions.