Oregon's election is on May 20th and if you're registered to vote you should have received a ballot.
There are local offices and local measures on the ballot. If you have not received a ballot contact your county elections office.
If you mail the ballot, it doesn't need a stamp. It can be postmarked May 20th, but needs to arrive by May 27th.
You can also drop ballots into county ballot boxes by 8 p.m. on the 20th.