Do you have my book?
http://www.apress.com/br/book/9781484214237ıt is all documented there.
I suggest you to get one.. This is a long story. All explained in Chapter 13. (Chapter 13: Oracle E-Business Suite 12.2 Performance Recommendations)
In general, you should configure the heap sizes for OA core, add additional managed servers to oacore if necessary.
As for Concurrents, you should configure the cache, sleep and manager counts. Also implement PCP if it fits your needs. Ensure the network latency between conc managers and db is tolerable.