"I'm tired", in the formal language, is 피곤해요 (pi-gon-hae-yo). You can say 졸려요 (jol-lyeo-yo), which means "I'm sleepy". To make these sentences informal, take off the 요 (yo) and they turn into 피곤해 (pi-gon-hae) and 졸려 (jol-lyeo). If your name is Johee, your name would be 조희 or 조히.