The process is similar to getting a pilot certificate. :
a knowledge test (written) then a practiacal test. The knowledge test is avaiable in 3 flafors: recip, turbo prop, or turbojet. The practical test consistes of an oral examination and a flight test. THe practiacl test can be accomplished on an approved simulator.
There are three ratings on an FE ticket: Reciprocating, turboprop and turbojet. there are no type specific ratings. each rating requires a knowledge test and a practical test. If you have a recip rating, you can operate a DC-6, or a Constellation or a stratoliner without additional certification. Obviously, type specific training would be a good idea. If you already have, say, a FE ticket with a recip rating, and you want to add a turbojet rating, you take an abbreviated version of the turbojet knowledge exam, then a practical test on a turbojet.
An A&P is not required.
You can qualify by:
having 3 years experience in aircraft Maintenece with a year working on aircraft of over 800 Hp. NO A&P is required.
Being a graduate of a 2 year Mx program that has 6 months of training one aircraft of 800 hp or more.
Having a commercial pilot certificate with instrument rating.
having an engineering degree and 6 month experience maintaining aircraft of 800 hp or more.
200 hours of flight time in a transport category aircraft
or
100 hours of flight time as a flight engineer.