Hmmm, sorry for misunderstanding your question. As far as I know there is no easy CSV file upload method to create self-enrollment keys in courses.
This can be done with a script and MSQL queries, so it will require someone with programming knowledge. The table you need to access is mdl_enrol.
I suggest creating self enrollments in a couple courses, then look at table mdl_enrol to get an idea of the data you need to supply.