I'll probably need more details but if I understand, you have Data on some database and you want to import\synch with CRM.
Is this going to be an operation that will be repeated with a schedule? like every day at 12:00 am?
If yes, you may be better using SSIS with and adapter or the SSIS script along with CRM sdk
example:
http://a33ik.blogspot.co.nz/2012/02/integrating-crm-2011-using-sql.html
or you can write a console application that will run with windows task manager
http://msdn.microsoft.com/en-us/library/gg695803.aspx
If it is something to do just once you can export the data from the databse as a CSV and import using the CRM data import
https://community.dynamics.com/crm/b/crmsoftwareblog/archive/2012/05/31/microsoft-dynamics-crm-2011-improves-data-import-wizard.aspx
Now, how do you distinguish between data that goes to contact and data that goes to contact?
the data import is pretty limited on distinguishing. you may need to go with the first 2 options or create different CSV files, one for accounts only and one for contacts only. you can separate using T-SQL and save the query to do it again
I Hope I could help. If I have answered please mark as 'Answer'. If was just helpful, please vote. Thanks and happy coding! Bruno Lucas, http://dynamicday.wordpress.com/