This is a regular verb. It follows the conjugation pattern of the verb falar.
Present:
A Ana encosta na parede.
A Ana encosta-se à parede.
Ana leans against the wall.
Preterite:
O Miguel encostou a bicicleta na porta.
O Miguel encostou a bicicleta à porta.
Miguel leaned the bike against the door.
Conditional:
(Eu) encostaria isso aqui.
I would lean it here.