You can use the “For Each” or “For Each Row” activity. If you use the regular For Each, just change the ArgumentType to DataRow and put datatablevariable.AsEnumerable.
If the workflow you want to invoke is the same for each row, then just do this:
Invoke Workflow File
If the workflow you want to invoke is different for each file, then use a Switch activity, so you can use a different Invoke based on the value of the row item.
To use the row variable within the For each, just do
row("columnname").ToString, where row is the variable name used for the For each (which can be any word actually, so don’t be afraid to be more specific than just row or item).
I hope this answers your question. Also, explore the Academy which I think is linked on the top of the Forum’s home page; this will go over loops I believe.