It's one of the worst experiences your phone is ever liable to experience: falling into water, whether it's a swimming pool or a sink. There are any number of situations in which your phone can become wet and short-circuit. The question is, what can you do about it?
The Rice Method doesn't work
So many sites on the internet claim you can desiccate (ie, dry out) a wet cell phone or other electronics by immersing it in a container of dry rice that it's generally accepted as common knowledge--except that it doesn't work. There's little evidence other than anecdotal reports that you can fix wet electronics with rice, and a few fairly scientific tests have essentially debunked this entirely.
Yes, phones have known to dry out and function again, but it's unlikely that rice has anything to do with it--it's more likely that the electronics in question just didn't get wet enough to really be damaged to begin with.
The bottom line: There's little hard in trying this (other than a container of wasted rice) but there really isn't any point. Rice doesn't work.
If you insist on trying the Rice Method, it's pretty straightforward. Turn off the device immediately, take off the battery cover and remove the battery (if possible). Dry everything with paper towel, and then submerge all the components in dry rice for about 3 days. Then put it all back together and turn it on.
Desiccant packs work more reliably
A better solution is to use any one of a number of commercially available desiccant packs designed to help recover your electronics if they get wet.
Kensington , for example, claims that its EVAP Rescue Pouch is "700 percent more effective at removing moisture than rice." Similar products include the BHEESTIE Bag and the Mach Speed Yikes! Phone and Tablet Rescue.