When a verb or adjective ends with -하다 [ ha-da ], change 하다 to -했어요. -하다 is verbs “to do”. Many nouns can be made into past tens

• 일하다 [ il-ha-da ] + -했어요 = 일했어요 [ il-hae-sseo-yo ] - to work
• 공부하다 [ gong-bu-ha-da ] + -했어요 = 공부했어요 [ gong-bu-hae-sseo-yo ] - to study
• 운동하다 [ un-dong-ha-da ] + -했어요 = 운동했어요 [ un-dong-hae-sseo-yo ] - to exercise
• 전화하다 [ jeon-hwa-ha-da ] + -했어요 = 전화했어요 [ jeon-hwa-hae-sseo-yo ] - to make a phone call
• 요리하다 [ yo-ri-ha-da ] + -했어요 = 요리했어요 [ yo-ri-hae-sseo-yo ] - to cook
• 운전하다 [ un-jeon-ha-da ] + -했어요 = 운전했어요 [ un-jeon-hae-sseo-yo ] - to drive
• 수영하다 [ su-yeong-ha-da ] + -했어요 = 수영했어요 [ su-yeong-hae-sseo-yo ] - to swim
• 청소하다 [ cheong-so-ha-da ] + -했어요 = 청소했어요 [ cheong-so-hae-sseo-yo ] - to clean
• 빨래하다 [ bbal-lae-ha-da ] + -했어요 = 빨래했어요 [ bbal-lae-hae-sseo-yo ] - to do laundry
• 복잡하다 [ bok-jap-ha-da ] + -했어요 = 복잡했어요 [ bok-jap-hae-sseo-yo ] - to be crowded