How do I find out about training to take care of someone who is bed ridden?

Anoher vote for Therapy in the home (if your insurance or funds cover).

Physiotherapists can help maximise the mobility a person does have plus show the caregiver how to assist in the best way (safe for both of you).

Occupational Therapists can prescribe equipment to help. The right type of equipment can make a huge difference. Big things like walking frame, lifting machine, hoist, recliner chairs - these can really save your back! Even smaller equipment eg shower head on a hose, long handled sponge, showhorn etc can save your back when helping everyday.

CNAs as mentioned know the daily personal care skills & tricks.

Being open to learn new skills yourself is a step not all can take.

Congratulates on your mindset already.

If the person is a veteran, check with the VA for caregiver education and help. You don’t have to be a veteran yourself nor do you have to be living with the person.

If the person is eligible for Hospice the CNA will or can do a wonderful job teaching you all sorts of things that will make life easier.
From changing a brief(aka diaper) in bed
changing the sheets
giving a bed bath
changing positions.
And Hospice will order the equipment that you would need to make things easier for you and the person you are caring for.
If they would not qualify for Hospice the doctor can order a Physical Therapy session in the home and the therapist can teach you some things.
If you need to learn something YouTube is great with video how to's for all sorts of things.

See if the persons Dr can order in home therapy. The Therapist could then show you how to do things safely.