Déstapate comes from the verb destaparse, meaning to 'uncover oneself' or 'reveal oneself'. It's a less common, more evocative way to tell someone to be open and vulnerable.
In the song, the singer is frustrated by their partner's emotional distance and lack of communication. They implore their lover to Déstapate y muéstrate (Uncover yourself and show yourself), urging them to drop their guard and express their true feelings rather than hiding them.
Esteman opens sure of himself, no hesitation. 'Simple, tan simple' [Simple, so simple], he sings, 'Que eras todo eso' [That you were all that], 'Que quiero para mí' [I want for myself]. It's stated as fact before the song gives you any reason to doubt it.
Then it turns. He watches the other person keep drifting off: 'Que cuando te alejas' [That when you go away], 'Te pierdes corazón' [You get lost, darling], 'Y no das señal' [And you don't give a sign]. The hook names exactly what that does to time, 'Parece tan eterno cuando no estás' [It seems so eternal when you're not here], and by the end he's done waiting on it: 'Si vuelves ya no voy a estar' [If you come back, I won't be here anymore]. The last chorus isn't a plea so much as a deadline, 'Hoy dame tu amor' [Today give me your love], 'Mi corazón no puede esperar' [My heart can't wait].