You can leave an open application to the open application pool by registering with email address and password, and filling in the pages of the application. Hiring managers are able to screen the open pool for matching applicants to their open positions. Note that if you leave onlyan open application (you do not apply for any individual position), you are allowed to attach only one attachment (CV) in your application.
You can also leave an open application while filling in your application for an individual position, by selecting "I want to leave my open application" in the recruitment system.