The Approximate address is a search field which uses Google places to search for an address based on your what you have typed. 

Type into the box, then select a matching address from the dropdown.  

This makes the address search very quick.

If you see animated circular arrows.  This is an attempt to ask the browser for it’s current geolocation. 

This is often turned off by privacy conscious users, so it is entirely optional.
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But, it is critical to know where this burn is to be registered, so the address field is a required field