a review?

One of the PIs in my lab asked if I would like to review a paper with her today. Naturally I said yes.  I mean, its something new. I’ve never done it before. Actually, I’ve never written a paper before (and now I’m writing one) and I figured it was a good idea to learn how to review papers too, if only just so I know what people do when they are reading my paper. But its kinda scary though. I mean, a group wants their results published.  They worked hard get to the writing stage and now whether or not it gets published is boiling down to someone like me reviewing it.  I”m actually kinda scared.