How should I approach to these companies to become a Freelance Manpower Supplier?

Myself Swarup Bose, a data entry operator, working in an MNC, based in Kolkata for full time. And here is one of my company policy of recruitment, if you refer a candidate and He/she gets the job and worked for a month, you will get a referral bonus. I have successfully referred to some candidates already. And I know there are several other companies who are doing the same.
I recently decide to work as a freelancer recruiter besides working as a data entry operator, to supply manpower to those companies and want to get paid from them. I don't want to charge the candidate even a single penny. And there are several companies who hiring Telecaller, Data Entry Operator, Sales Executive and I know these companies. But my question is, how should I approach to these companies to become a manpower supplier and how I will get paid. I mean when I refer to candidate to my company, I can directly go to company HR for referral bonus, but how should I approach to these companies to supply manpower and get paid. And I am confused to mess up with this stuff.

Dear Swarup Bose,
Whenever the vacancy arises in your company, if you refer the candidate to fill the vacancy, and if it is as per the "Employee Referral Policy", then nothing wrong as such. However, over a period of time, you have acquired the expertise to refer the candidates and you wish to encash on this expertise by recommending the candidates to other companies as well. However, it could be a conflict of interest. Therefore, please check the terms and conditions of employment in your appointment letter.
Most of the companies mention explicitly that dual employment is prohibited. While freelancing is not direct employment as such but then for your referral services, you will receive the remuneration. Your company may construe it as a conflict with the terms of employment. Therefore gentleman, tread cautiously. Your zeal to earn a secondary income should not impact your primary income itself.
Thanks,
Dinesh Divekar