Well to manually import data from a CSV file into a database such as Access you could get into the database, import the file into a new table, and then run an append query.
If everything is online then let the CSV file be a recordset that you go through record by record to read and let the regular database table be a recordset to go through record by record to write. You could delete all the related records in the regular database first and then add them all back one by one.