How do i have sex on top?

yesterday i had sex with my boyfriend, and it was the first time i went on top. the whole point of me going on top was so that he didn't do all the work, but i didn't know what to do, so he still did all the work! whenever i tried to take over, he just kept slipping out of me, so how do i do it? moving forward and backwards while sitting upright didn't work. help?