How to Add Auto Increment Field to Import Table

i am importing a table and would like to add an id column auto-increment but i dont see that option.

whats the best way to add an id field, before i import (within my excel or csv file) or after i import (how is this done?) 

thanks

Thanks Roger, it would be a nice feature to have, maybe also in the Query Builder to select a checkbox to add column with auto_increment.

thanks for the attention.