Go through an agent, or start filling out the HNA overseas e-application. They will get back to you.
Agent vs HNA Overseas. HNA Overseas is Hainan's in house "agent". My observation, the regular agents were more on top of things during the medical, the HNA folks seemed less experience, were distracted with regular work and keeping tabs on the progress of the other pilots. There may be other benifits with HNA down the road, I don't know. What I do know is that there are slight differences in the offered contract. Specifically one agent says $200/hr over 720hrs overtime. The HNA contract is $250/hr overtime. HNA provided the same contract to all agents to keep things the same, what the agent then offers is up to them.
If you go with an agent, make sure you know what you're signing.