Where and how do you do this? Seriously?

I'm AFAB but want to present neutral. I recently rebooted my work wardrobe into all black and simple, and this made me feel better, although, in hindsight, everything available still had some kind of frills/lace/emphasis on curves/etc.

I want clothes that are comfortable.

Am I supposed to go into men's stores? I don't know how to even begin thinking about that and the thought makes me feel helpless and terrified.

Am I supposed to spend 400 hours digging through every rack at every woman's store in hopes of finding one, well, piece of something, that maybe kind of works? I don't know?

I really don't know. The only thing I know is that I want to set my current wardrobe on fire. Help! What do you do? Thanks.

Online.

I used to do all of my shopping online once I knew where I liked to shop and how the sizes fit. But because my goals are so different, I think it would be advantageous to try things on first, rather than dealing with the hassle of returns. Some places online aren't return friendly, or the whole process can take weeks/months (like Zulily). 

Unless you happen to know of some magical androgynous online retailer with an amazing catalogue...... 

I'm also so ugh about my body right now, I'd rather throw something back on a rack, than spend time dealing with online returns because the whole process would just mean more frustration.

You can try thrift stores, you'd be surprised about the finds there. Places like Target or Walmart can help with more "casual" clothing [in the men's department]. You don't have to go into men-specific stores if you don't want to.

You can also try altering your own clothes. I did this when I decided that I wanted to transition into a more androgynous appearance but didn't have any money. Still don't but anyways; there's a lot of resources [Youtube is Superior, blogs like on tumblr can help as well, it's just a matter of finding them], for learning how to do simple sewing alterations. I simplified a lot of my own clothing by removing lace/frills/what-have-you.

You don't have to wear all black by the way. Since you're AFAB, anything that leans to the masculine will look more androgynous to people so you might want to avoid anything distinctively feminized [low-cut v-neck collars come to mind, as well as pink colors].

I like to present myself in a more androgynous fashion too so I get the struggle.

There is no "supposed" here.  You can shop wherever you want.  No one will give a second thought if you shop for men's clothes, either in a men's wear store or a department store.  Half the men in North America probably couldn't buy themselves a shirt if they had to.  Their wives buy their clothes.

However, you may still find it easier to find androgynous clothes in women's stores.  Society considers it fine for women to appear masculine, but totally unacceptable for men to appear feminine.  So men's clothes will mostly be unmistakably masculine, whereas some women's clothes can be in the middle.

When I was shopping for androgynous clothes, I went to women's stores or departments.  Plain women's slacks, a women's top that isn't particularly colourful or frilly, and sneakers aren't going to scream feminine.  If you want to present more masculine than that, try jeans and a T-shirt, the uniform of half the male population.  They can be women's cut, to avoid looking all the way masculine, while still being something that a male would wear.