Each company may have different procedures that they (may) require. Back in the 1990's, there was 1 company that trained them, but (required) that they get their AIC (Associate in Claims) w/in 2 years.
I was trained in 1 company that did it (2) ways. With me, a co-worker trained me and she was my "mentor" that oversaw my training, where as other people that were hired, went through 6 weeks of training.
In another company, they had the new hires in classes/training for (6) months, but that was due to the fact they were being trained in (commercial) claims vs (personal) claims.
But depending in (what) state you live in, then in (some) states must pass (tests) to be licensed to handle claims. So could end up taking classes from anywhere of 6 weeks to 6 months.
In almost all cases, then most companies to train you, will expect that you have a college degree.