SRX240H - irb or multiple vlans

Hello, I'm a newbe and I'm just starting my adventure with SRX`s;) 

My hard: SRX 240H (JUNOS Software Release [12.1X44-D40.2]

I would like to set up several subvilans or subnets on one physical interface, e.g. ge-0/0/6.
Here is a description of my idea.  Something like multiple vlans. But I read that it can be done with irb.

I made two irb's but I don't know how to connect them to one VLAN or physical interface. Can you give me a hint? Maybe I made a mistake.

}
irb {
unit 1 {
family inet {
address 192.168.200.1/24;
}
}
unit 2 {
family inet {
address 192.168.201.1/24;
}
}
}