Add the sixth parameter to the client program:

First parameter: serverIP
Second parameter: simulateOption: real/ideal
Third parameter: T (for simulating the throughput)
Fourth parameter: percentage of active clients for ideal mode
Fifth parameter: start client user ID
Sixth parameter: number of users assigned to each client

sbt "run serverIP:port 0/1 T 0.1 startUserID numWorkersEachClient"
For example,
if the server handle 1000000 users, then in each client you should run
sbt "run 10.244.33.144:9001 0 1 0.1 0 500000"
sbt "run 10.244.33.144:9001 0 1 0.1 500000 500000"