Hello Eduardo,
you may access the optimization popup window once you select calculate. Choose Optimization tap, then click on MPO and select insert (you may double click on it to have the same effect).The advanced and parameters can be set in this window.
There are some examples in the example library that can used as a reference for your project on optimization. one of them can be found at the link below.
C:\Users\xxxxxxxxx\Documents\OptiSystem 15.2 Samples\Optical amplifiers\Fiber Length Optimization.osd
regards,
Ahmad