This is money. Real money.
Do not ask this on a public forum, and if you do, do not listen to any replies.
Talk instead to the people providing the service:
Element Payment Services[
^]
1) They will be used to this, and will know the procedure well.
2) If they don't, use someone else as the chances are they are cowboys!
3) Any detailed advice you get from a public forum on how to handle credit card transactions must be treated with extreme caution: Is the person giving the advice leaving any holes though which he can syphon credit card information or money?
You MUST do this properly. If not, you may find yourself, personally, liable either for any monies lost, or criminal prosecution, or both!