Hi

from my opinion a good start is if you

read some theory about open water swimming..
https://www.amazon.com/Triathlon-Swi...dp/1931009074/

watch the TI DVD
https://www.amazon.com/Total-Immersi...dp/B003X2O79W/

get a swim tracker that tracks and coaches your performance
http://fitnesstracker24.com/10-best-...-for-swimming/

get good and comfortable swimwear (goggles!) to avoid distraction while swimming
http://pooladvisors.net/buying-guide...mming-goggles/

and then practice yourself :-)