If you are interested in one specific bedroom, you can apply for the bedroom. After filling in your information and finishing your application, you will be able to chat with the current housemates from the house. They will then be able to invite you for a visit in the house. The current housemates 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 housemates, the property manager would be available to help through the help center or the Coloc Housing Chat on your dashboard.