Macam mana nak introduce bubur nasi to 7 months old baby? Please help!

First food baby makan (6 months) is Cerelac Rice/Beras (advised by Paed) sebab baby susah nak buang air besar. Now nak introduce bubur nasi tapi dia tak makan langsung. Tapi kalau buat Cerelac + Carrot/Broccoli dia makan pula.