Go to My Account Settings > Custom Document Templates
In the Custom Document Template tab, you can create a new template by adding the title, and click + Create Template. You can either do a blank page and create your own, or you can upload a word document that has already been created.
Once the new template is added, you can click on the pencil icon to edit. There are several tags in the edit screen that you can select to indicate which type of form it is.