3-4 LB sub help

I am using 3-4 PB and am trying to use my #2 RLB as my 4th LB on the field.

I have tried changing them around on the depth chart.

I have tried changing both players positions.

Is there something I'm doing wrong? Is there a default LB position player that gets added for 3-4?

Thanks in advance

No1 knows?

In the 3-4 defense you will have 3 defensive linemen. They are the LE, RE, and starting DT will be the nose tackle. The LB's will be the ROLB, LOLB, and the starting MLB and the second string MLB will play the inside linebackers. Have any ?'s just ask.......