This is the 2383rd most frequent Catalan word.
ocupar
To take up, occupy, or fill a space or position.
In this sentence, 'ocuparan' represents future tense and signifies taking residence in a physical space.
Els meus veïns ocuparan l'apartament de la primera planta.
My neighbors will occupy the apartment on the first floor.
Here, 'ocupava' is in past tense and indicates something taking up time.
Aquest llibre m'ocupava bona part del temps lliure.
This book occupied a good part of my free time.
'Ocupar-se' here is a reflexive verb form used to express taking responsibility for or addressing something.