How to burn lower belly fat and leg fat in gym?? please help?

Hello iam 18 ,weigh 65kg ans height 5'7,ok first iam not fat and dont look fat at all ,but i got fat on my belly,its totally flat but i hav a layer of flabby fat which i hate,and my legs i need to tone them quite good,i wanna build muscles but also reduce this flabby fat how?? How much cardio should i do on treadmill?? Please help