Hello Dylen :) For this particular phrase, you'd say 私はお風呂に入っています。お風呂にいます would also be understandable, but while I lived there, I hardly ever heard it being used.

Hi Dylen! So, the difference between in います and あります is a bit more complicated than just the living thing or object ;) Let me explain. I always explain to my students that います is for things that have LEGS in their natural state, and あります is for things that don't have legs in their natural state. Why? For example, a tree is a living thing, but it would go with あります、because it doesn't have legs. Also, a ghost (like a spirit of someone who passed away), though dead, would go with います。Just to show you this idea, what do you think would go with Frankenstein? Frankenstein is a monster... Not sure if it is "living" or not, but he has got legs, right? So, it would go with います。Funny, huh :) Kallhandra brings up an excellent point in her comment! if you want to say "I am taking a bath", you would definitely say "お風呂に入っています。" You would say "お風呂にいます" if you are purely trying to explain the location at which you are. For example, someone calls you while you are cleaning the bathtub. They ask "Hey, where are you? I hear a lot of echo!" and you want to communicate that you are currently in the bathroom (not necessarily taking a bath). Then, you would say "お風呂にいます". Hope this helps! Cheers!