You are writing JSL to make a data table and you are not sure how to script creating the table and columns.
Make a data table, using JMP's GUI, that looks the way you want. Add the numeric formats (dates, etc) to the columns that need them, and formula columns too. Then delete the rows, or leave the rows with the default data you need. Finally, use the red triangle and pick "Copy Table Script". Go back to the script editor, type "dt =" and paste the script.
// typical JSL for an empty table with one column
New Table( "Untitled",
Add Rows( 0 ),
New Column( "Column 1", Numeric, "Continuous", Format( "Best", 12 ), Set Values(  ) )
Use dt = New Table(...) to get a variable that you can use to reference the table. Look in the scripting index to see the commands you can send to the table using dt.