I found the job listing on Craigslist and sent them my resume.
I received a call to set up an interview appointment.
On the day, they asked me simple questions about my experience with languages and availability to work. Then I took a language exam that consisted of translating medical terms from one language to another.
Then, she told me I passed and that once I was registered on the interpreters roster ($50 fee), I'd start receiving cases. The very next day they called me asking me if I was available to go interpret at a hospital.
Piece of cake.