do that (URGENT)? I don't really have a lot of tools, but could I use those big scissors? Oh and could you tell how to do it? Like what should I avoid?

Totally different task. If she can't tell you, don't do it. Some bushes and shrubs are trimmed from the outside with hedge trimmers (big scissors) but trees are normally trimmed with loppers where you go back down a branch and take it where it comes off another branch. Different trees are different.

Here is a tutorial:
http://www.ehow.com/how_3642_prune-citrus-tree.html