You can travel to the Otherworld by entering trance state and journeying in spirit form. There are many ways to induce a trance, such as using shamanic trance rhythms or drumming, or by using special plant medicines (only under expert supervision). Of course, you will also have to still your mind, release anxieties and distractions, etc. while doing this. Once in a trance state, envision a peaceful place in nature as vividly as you can. Then visualize an opening leading downward into the Earth (a tunnel or burrow downward, a body of water, etc.) and go into it. What this meditation/visualization does is triggers spirit travel into a part of the Otherworld inhabited by nature spirits, including totem (or "power") animals. Once there, if you are looking for your animal guide, ask around until you find them, there are other helpful spirits who can aid you.
Here's a place where you can get a shamanic drumming track for free. It will help induce a trance.http://www.shamanismcanada.com/drumming.html