Sleep apnea secondary

Im planning on filing a sleep apnea claim secondary to anxiety I've been having trouble staying asleep for a while now even while I was in service and figured it might be just waking uo being paranoid about a casualty on the ship or being late or something going wrong. It still kept happening after I got out and ive been out since Oct 2018. Do I just file the claim and I'll get a cp exam and they'll do a sleep study or would I have to get the sleep study done prior to?