This chapter of the guide to Dragon Ball Z: Kakarot has a walkthrough for the Telekinesis Training side quest.
Time frame: From Attack of the Saiyans - Episode 3: Survival 101 to Episode 3: Survival 101
Reward: 489 EXP, D medal, Bronze Compass, Mega Mass Lvl 1
Where to start: Central Plains Area, as Piccolo.
Talk to Chiaotzu and then fight him. Tien will accompany him. Your task is to defeat both opponents.
Once the battle is over, talk to the quest giver. This will complete the mission.