Display posts for specific blog

Hi i am using vintage immersed free theme for this month september 2013
so i have one small problem i have create seperate pages with three different blogs named tech food business so when create a post it displays on all three blogs i want tech post to be displayed only on tech blog ,food post on food blog ,business post to be displayed for business blog any help would be great.i am not getting logic as i am new to wordpress.