If you are interested in one specific room, you can apply for the room. After filling in your information and finishing your application, you will be able to chat with the current roomies from the house. They will then be able to invite you for a visit in the house. The current roomies in the house are the people deciding who will be accepted to their home.
In case you can't seem to get a hold of your possible future roomies, the property manager would be available to help through the help center or the Coloc Housing Chat on your dashboard.