Here are some ways to find testing resources that you may be seeking:
You can enter your zip code and it gives you all the surrounding area locations doing testing, hours, requirements, who qualifies (symptomatic, asymptomatic, known exposure, kids, adults, etc.), rapid v. not rapid testing, number of days to receive results, phone number or website address, how to schedule, etc.
Another resource from Multnomah County:
Multnomah County is doing testing regardless of health insurance status, immigration status, and you don’t have to live in Multnomah County. MultCo also goes though what to expect if you test positive in terms of follow-up calls, contact tracing, etc.
For known exposure, it’s recommended to wait 3-4 days if asymptomatic prior to getting tested to have the best chance of catching it. Symptomatic infections should get tested ASAP.