A Naturopath is a doctor who uses natural medicines (botanicals, herbs, manipulation, homeopathy, etc) for healing. They can also prescribe some medications. Their degree is an ND and they go to school 4-5 years after attaining a bachelors degree just like MD's do. Most ND's have homeopathy training and prescrible homeopathic medications.
There is no separate certification for homeopaths in the US so usually you have to go to an ND if you want a homeopathic visit. Some ND's get more post-graduate training in homeopathy than others and some base most or all of their practice on homeopathy.
To find an ND, go to www.aanp.org
Make sure you go to a naturopath that has gone to one of the accredited schools and has not got a mail order degree from a corerspondence college like Clayton. The AANP website only lists properly accredited ND's.
A DO is an osteopathic doctor and some are more holistic but these days, most are no different than MD's.
Hope this is helpful!