How to advane to a new position in a firm?

Hello. I am currently working in one department of the firm (let’s call it department nr.1) and now another person in another department (let’s call it department nr.2) has decided to quit. I have told my current manager in department number 1 that I want to try some of the work in department nr.2 when the person in department number 2 quits.

My manager in department nr.1 told me that he was going to tell others in the firm about my wish to work in department number 2. I also told the manager in department number 2 that I wanted to try some of the work in department number 2. However the manager in department number 2 then told me that he did not need any new people in her department at first, he told me that whats more important is to transfer a job task from department 2 to department number 1. What can I do to transfer to department number 2?

Thank you for answers.