DNA testing is done via Optigen (for PRA) and Antagene (for FN). How old is Poppy? FN affects juvenile dogs, generally between 6 months and 2 years old. In all honesty as you want to test just for your own peace of mind unless you're really worried I don't think you stand to gain much from having her FN tested; FN is rare and even if the worst happened it would be evident while she was still young.
For PRA testing you can either attend a 'clinic' where bloods are taken on the day or you post bloods in to the coordinator who then sends them off or you can have the bloods taken and post them off yourself. In both cases you can order and pay for the tests on the Optigen website. The test is about £120 plus vet costs and postage (to America). The Optigen website contains all the information you need for ordering the test
http://www.optigen.com/
