Here is the address I will use. It's the church's address, so make sure to have my name somewhere on the envelope/package. But, here it is in English and in Korean. If you feel like sending mail, you can just print the addresses out and tape them to the envelope/package.
Onyang Oncheon Methodist Church
Asan city, Chungnam-do, Oncheon2-dong #149-47, 336-012
충남 아산시온천2동 149-47번지