I moved here in 2008 and brought a shotgun with me.  I never registered it here and it has sat in my closet for the past seven years.  I would like to sell it.  What are the ways to do this legally?

Assuming you're on Oahu, meet the buyer at HPD with it.  Tell HPD you have an out of state firearm you want to transfer.  You should try and arrive before 2:30 to make sure you have time to do the out of state registration.  They will likely require you to do the out of state registration first so they can run the proper checks on it.

Then you can immediately transfer to the buyer if he/she has a valid long gun permit.  If the buyer has no permit, have the buyer apply first.  If you meet the day that permit is ready, it'll save the buyer a trip, too.

As far as anyone is aware, the firearm was stored on the mainland until you had it shipped to Oahu to sell.  No sense in volunteering irrelevant information.

I moved here in 2008 and brought a shotgun with me.  I never registered it here and it has sat in my closet for the past seven years.  I would like to sell it.  What are the ways to do this legally?

Go down and register it before you try to sell it, to be fair to the your future buyer. Don't pass your problem to the buyer..
Just register it as if it just came from the Mainland..

Thank you for the information.  I will go down and register it.  I figure I might as well sell it to someone who will use it.  I purchased it when I was in Alaska for my fishing trips.  Only fired it a few times at the range.  I should have registered it when I got here but out of site out of mind.