to show up, to show one's face
Faz tempo que ele não dá as caras por aqui, será que mudou de cidade?
He hasn't shown his face around here in a while, did he move to another city?
The image is transparent: your face cannot turn up somewhere without you, so "to give your faces" (dar as caras) simply means to show up in person and let yourself be seen. The curious plural caras, where one person has only one face, echoes card-game talk like dar as cartas ("to deal the cards") and mostrar o jogo ("to show one's hand").
Falando's Idiom Trainer teaches you to recognize idiom meanings and create sentences using them, so you can speak like a Brazilian.
