Register first so you can use contractor account features without completing a long profile form. Your permanent profile address is reserved now; build your recruiter profile later, when you have time.
There is no need to complete your professional profile before registering. Verify your email, create your password and use your Contractor ID. You can then add skills, experience, rates and preferences later for better matching, recruiter visibility and a stronger profile link.
Only the essentials are required. Your professional profile is a separate step and stays private until you complete it.