Learn Spanish (Latin America): Son las ocho y mi hermana se despierta. - It is eight o'clock and my sister wakes up.

The verb here is despertarse (to wake up). It is a reflexive verb, meaning the action is something the subject does to themselves. Without the se, despierta would mean she is waking someone else up. The se shows she is waking herself up.

Can I attach the se to the end of the verb, like despiertase?

Not in this sentence! When a verb is conjugated to match a subject (like despierta matching mi hermana), the reflexive pronoun se must go directly before the verb. You only attach it to the end if the verb is in its unconjugated dictionary form, like despertarse.

The dictionary form is despertarse. Why is it spelled despierta here instead of desperta?

This is a stem-changing verb, often called a boot verb. In the present tense, the letter e in the middle changes to ie for most forms. Since the subject is mi hermana (she), the verb takes the stem-changed form despierta.

Why do we use the plural Son las to say "It is" when telling the time?