Hi Alexis,

You can find parameters description and their usage at the following places:
Valentina Reports Parameters
SetParameterValue

In short.

Parameters can be defined:

• inside of the Expression Field in your report
  
(e. g. Year: $P(param1=2016))

• inside of the source query of your report
  
(e. g. SELECT * FROM t1 WHERE f1 = $P(param1=2016))

Later in code you can set the parameter value or leave a default:

dim theReport as VReport = my_project.MakeNewReport( "report_1", "sqlite://c:/somedb.sqlite" ) 

theReport.SetParameterValue( "param1", "2017" )