I used to study at "SUN" college there, you need to take the MRT to Muzium Negara and switch to KTM at KL sentral. Please make sure you arrive at the KTM platform before 7:00 a.m because once you missed the 7:00 a.m. train, your next train will be arriving at 8:10 a.m.
The train you will take you to setia jaya station and from there switch to BRT and disembark at Sunway Lagoon station.