It's easy and will help you be a better coach. Everything you need can be found on the Positive Coaching Alliance website at http://positivecoach.org
There is even an online version of this certification course that you can take at https://www.positivecoach.org/DGC.aspx
The cost was $25. It took me just over an hour to complete the whole course (but I've been through PCA training twice before). It would probably take a new person about 1.5 hours to finish it successfully. One caveat -- be very careful on the test because once you click submit for a question, you can no longer change your answer (I mistakenly clicked too quickly on one and could not go back even though I knew I had mis-entered my answer when I had clicked submit). Still I got 90% (I validly missed a 2nd question with an incomplete answer).
The course was pretty well put together. It has well written text, good examples, some short videos, interactive worksheets, an overall table of contents, progress indicators, PDF handouts you can download and print if desired, and a concluding test where if you pass (80% or better -- at least 16 of 20 questions correct) you get an instant online certificate. I think it is worthwhile for very coach to become certified at least once if not yearly.
Coaching is challenging and coaches deserve to be well trained.