I've sent to them previously. You don't need to contact them beforehand. Check out
this document from their
website. You can order the tests yourself, you only need a phlebotomist to draw the blood, separate the serum and transfer it to a transport tube.
Remember to email them the tracking number after you've sent the package. They send the invoice via email after they have analyzed the sample, and after it has been paid they email you the results. An overview of the shipping rules that exists for sending blood/serum samples can be found
here. I've sent packages labeled as "Exempt human specimen" successfully using FedEx. You can get a 40% discount on all shipments if you register a FedEx account. But double check if the discount is applied, because it wasn't for me at first, I had to call them to sort it out.