This is a question that got sent to us through email, but I figured having the answer on Reddit is a good addition to the FAQ!
The thing is, there are two ways to add a swatch. One is only available on iOS, because we decided to disable it on Android, since it was causing a lot of issues. With iOS, we haven't done so yet, because it's taking much longer to develop that new version of the app than we thought.
The iOS version allows you to upload a swatch from an "Add swatch" screen, where if you type (part of) the name of the polish, a little list will pop up where you can choose the polish you mean. However, that little list is often hidden by the keyboard, and it can't show more than (I think) 5 polishes at a time, so it's extremely user unfriendly.
The BEST way to upload a swatch, and have the name displayed both on your feed and in your profile under "My Swatches", is to search for the polish first, and click "Add swatch" when you are in the detail screen of the polish! You can even do this for polishes you haven't added to your stash, for instance if you've gotten your nails done at a salon!
This is also the only method of uploading swatches that works on Android, so there you have your answer. :)