Gravity Forms provides merge tags that allow you to dynamically populate fields in forms using information about a user logged into your website. In order to use information about a user completing your form, the page your form is on should be private. This feature can be useful if, for example, you want to setup a newsletter subscription form. Using merge tags, you can auto-fill the name and email-address of a user so they do not have to.
Once logged into your site, click on Forms. There will be a some instructions on how to get started.