Before combining two databases or making any other major changes such as this to your databases, it's a good idea to back up your data first!

Method 1:
To import all of the records from one database to another, first open the database that you want to bring the other records into. Select File|Import Addresses and pick Envelope Manager format. Input the name of the database that you want to merge with the currently open database in the Import File Name box. Click OK to begin the import. The records will begin importing in record number order. The total number of records imported (copied) will display at the end.

Method 2:
If you want to keep the 2 databases separate for future mailings, create a new database and then import both of the databases you want to combine into it using the procedure above.