Chekov will be the navigator of the Enterprise, working under the orders of James T. Kirk.
Yelchhin will be joining Zachary Quinto and Leonard Nimoy who will both be playing the part of Spock. The rest of the cast is being selected presently in New York and London. The parts of Kirk, Bones, Uhura, Sulu, Scotty, as well as the villain and the captain of the film, The last two parts will require two great actors.
The details of the screenplay are not being publicized at this time, but there are rumors that we will see the crew of the Enterprise when they were younger attending the Starfleet Academy.