The good news is that all birds naturally close their eyes from the bottom up. If it has one good eye then you shouldn't need to feed or water the chick, it should be doing it by itself.
The bad news is not so bad because I don't know for sure what's wrong but if it's just an eye injury or irritation it should be easily overcome. At least both eyes aren't infected so you can guesstimate that it's not a symptom of disease, probably. Sounds like an irritation/injury to me anyway. Even if for some reason the eye is not recoverable, a one-eyed chicken often copes fine. I'd bet it's got something stuck under the lid or in the socket.
I would bathe her eye in something naturally antiseptic/ antibiotic/ antimicrobial/ antibacterial because 1) natural alternatives don't kill healthy cells too, and 2) I am obviously the sort who uses natural treatments in lieu of pharmaceutical ones. Someone who uses man made meds can advise you on doing it that way if that's your preference, but I don't have any experience with that. Personally I used chamomile with a chick that had a stab wound into the eye socket. The swelling pressed her eye down in the socket until her lid hung inwards, so it seemed she had lost the eye. (We called her Popeye). But after bathing her with that a few times her wound was clean and she healed fine with the eye moving back to normal position, and she grew up normal with two working eyes.
In general the advice would be to bathe the eye in something that will kill infection and soothe inflammation, whether you are using natural or man made things for the purpose. Rubbing at the eye is not a good idea, just soaking it so some seeps in through the lid. But that may need to be done differently with pharmaceuticals.
If the eye is actually swollen (are you 100% sure it's not just the skin around the eye being swollen?) --- then there is a chance the chick is deformed or has a tumor in its orbit or skull or on its eye which is causing it to protrude, or it could have a blockage in the eyeball preventing fluid being maintained at the right levels and causing it to swell. Damage to the eye could also cause this though.
Anyway, best wishes, hope she/he recovers.