How to parameter connexion to Big Query

Hi Sophie_, #"my_project" is only step name. You should focus on this part:

let
Source = GoogleBigQuery.Database(),
#"my_project" = Source{[Name="my_project"]}[Data],
Schema = #"my_project"{[Name="my_dataset",Kind="Schema"]}[Data],
my_dataset.kpi_Table = Schema{[Name="_kpi",Kind="Table"]}[Data]
in
my_dataset.kpi_Table

wich you can replace with your parameter without quotes:

#"my_project" = Source{[Name=myParameter]}[Data],

If you need additional assistance - be more specific please. What kind of parameter do you have/need. How exactly do you want to use such parameter. Add at least some screenshots data where you want to use it etc.