Instead of using table.insert, set the values directly on the table as if you were modifying data. The insert function can only add information, not modify it.
For example:
local testTable = {}
testTable[1000000] = {
-- table data here
}
You could possibly achieve this through stack table.insert() calls within one another but as the above user suggests simply indexing the desired key/field and assigning a particular value is the best way to go about this.