Acicálate comes from the verb acicalarse, which means 'to spruce yourself up' or 'to get all dolled up'. It's a fun, less common word for getting ready, like preening or primping before you go out.
In the song, Bad Bunny uses it in a cheeky, flirtatious way, telling the girl to get herself ready for him. This specific and playful use makes it a really interesting word to learn for understanding the nuances of modern reggaeton.
In this classic reggaeton track, Bad Bunny and Mora lay out a very tempting, very risky proposal. They're talking to a woman who's already in a relationship, but they can tell she's bored: "Pero él ya no te entretiene" [But he doesn't entertain you anymore]. The whole song is basically one big argument for a secret, one-time hookup.
The core deal is right there in the chorus: "déjame sentirte una vez, por si no te vuelvo a ver" [let me feel you one time, in case I don't see you again]. The plan is simple, at least on the surface. They'll spend one night together, and then she'll go back to her boyfriend and he'll go back to his life. No strings attached. But as the song goes on, the lines get a little blurry. He says he doesn't believe in love, "Pero no sé por qué ahora siempre que rezo / Le pido a Dios que me deje verte desnuda" [But I don't know why now whenever I pray / I ask God to let me see you naked]. It's a song about pure temptation and the complicated feelings that come with it.