Lève-toi vs Lèves-toi

Kiratiana, 

there is no imperative  ‘ Lèves-toi ‘ as all the - er verbs drop the ‘ final ‘s’ in the tu form of the imperative, as per attached lesson. Only the spelling as ‘ Lève-toi ‘ is correct.

 

“ Tu manges ton dessert. Mange ton dessert !

You're eating your dessert. Eat your dessert!

 

Note that for all verbs ending in -ER (including aller), the -s is dropped at the end of the tu form.
The other forms (nous and vous) are regular.

 Conjugate regular verbs in the imperative mood in French (L'Impératif)