To get the contact information of the client, you must create a service provider account (Helper account)

If you want to start message conversations with the client, you must first create a service provider account. Once you’ve created your account, navigate to the client’s job ad and you’ll see a button to bid on the job. You can then chat freely with the client.

List of conversations is available on your profile. There you will find a messaging system where you can continue conversations with the client.