Official ballot boxes can be found here: https://multco.us/elections/multnomah-county-official-ballot-drop-sites
After you've dropped off your ballot, you can check on its status here: https://secure.sos.state.or.us/orestar/vr/showVoterSearch.do
And... If you lost your Voters' Pamphlet, you can find it here: http://sos.oregon.gov/voting/Pages/current-election.aspx
All ballots must be received by your county elections office by 8 p.m. on May 17, 2016. Postmarks do not count.