Well, a little more info would be helpful. Are you trying to do level control in a well or tank? Are you trying to do flow control with a pump and VFD or valve (probably not, since you didn't mention any...)
Level control is pretty simple. Monitor the analog output, and when it goes too low (if you're trying to fill) or too high (if you're trying to empty) that triggers an output to the pump. You need to latch that in, with the opposite end of the analog output to break the latch when the tank is full (or empty).
Lots of ways to do it... if you were trying to fill a tank, you might try something like:
Rung 1 - If (AnalogOut < LowLevel) B3:0/0 On
Rung 2 - If (AnalogOut > HighLevel) B3:0/1 On
Then
----||-----|-----|/|---------( )----
...B3:0/0....|....B3:0/1..........O:0/0
----||-----|
..O:0/0
This is a pretty standard circuit... if this was a homework problem you're welcome. If you're doing this for real, then just start playing with your ladder package; it gets easier the more you do <g>.