Mommy skills needed

So I just turned 19 & I have no kids of my own. But my mother just got full custody of my two cousins one is 2.5 or 3 and the orther is 1 or 1.5. Due to my mom schedule I'll have to sit at home and take care of them until we find a reliable sitter. Back in 8th grade I took care of my lil sister but the parents did all the major stuff. This time I have to play mommy and I would just like some & any advice ...