If you do not use a specific format for the constituent ID:

Manually add the constituent ID to each record

OR

Download and run the Add Constituent ID plug-in. The plug-in adds the constituent IDs using the following pattern: BB + system record ID.

If you need to assign specific constituent IDs:

Add or edit the constituent IDs using Import.

OR
      If Blackbaud hosts your database:

    Contact Support and reference this article.