Here's a breakdown:
* "Levantarse" means "to get up" or "to rise"
* "Levantense" is the second-person plural imperative form, used to tell "you all" to get up.
Here are some examples:
* "Levantense, ya es tarde!" (Get up, it's already late!)
* "Levantense, niños, es hora de desayunar." (Get up, children, it's time for breakfast.)
* "Levantense y vengan a ayudarme." (Get up and come help me.)
Note: The "e" at the end of "Levantense" is added because it is a command addressed to a plural group.