EJB / EE :: Websphere Application Server 8

i want to use EJB 3 in my WAS8 application but it doesn't work.First of all i created an remote-interface:

import javax.ejb.Remote;
@Remote
public interface EjbTestRemote {
public void doSth();
}

Then i created a session bean class:

import javax.ejb.Stateless;
@Stateless
public class EjbTest implements EjbTestRemote {

[code]....

But now i want to call the session bean from a normal (no servlet, no ejb) java class but i doesn't work (NamingNotFoundException):

try {
Context ctx = new InitialContext();
EjbTestRemote ejbTestLocal = (EjbTestRemote) ctx.lookup("java:comp/env/EjbTest");
ejbTestLocal.doSth();
} catch (NamingException e) {
e.printStackTrace();
}