I am trying to import account and contacts from a SQL server database. By default SalesForce wants to use the account name. What's been happening is that when the account name from my SQL database doesn't match exactly with the name in SalesForce, duplicated accounts would be created. Even a tiny discrepancy like 'INC' vs. 'INC.' would create duplicate.

I read from some help articals that I could use an External ID as the matching criteira. But the import wizard's matching type only has Salesforce.com ID' and 'name and Site'. I did create a customized field for Account, and specified that it should be required, unique, and is an External ID. But this option is not there. 

So how do I get to specify I want to import by using the External ID as the matching type?

Thank you!