Do this in your own personal way. You can send a formal invitation for a referral via QuidProJobs subsequently.
Be genuinely grateful for every referral you get, even if it doesn't turn into business. You have to realize that someone took the time from their busy life to help you out. Thank them early and often. If you show real appreciation, there is a chance that those referrals will keep rolling in. At all times, keep your referral source in the loop!