The key time to speak about salary is when you know they want to hire you and you want to work for them, this normally happens after the 2nd face to face interview, depending on the hiring structure of the company.

When should you discuss salary requirements?

As a general rule of thumb, it's best to wait until the hiring manager brings up the topic. Best case scenario, a company lists the position's salary range on the job posting, and you can use that to best determine if the job and starting salary fit your needs before you even apply.

Should you wait to discuss salary until you receive a job offer?

Wait until you get an official job offer

Make sure you have an official written job offer before considering to negotiate your salary. This gives you more leverage since you know that they for sure want you as an employee. This also gives you a little more time to prepare for your negotiation.