When setting up a distribution database using the wizard, if you select the second radio button from the below screen you need to already have configured the distribution database on this instance.
Please keep in mind that because SQL Server express edition doesn’t have a SQL Server agent you cannot have this instance setup as either publisher or Distributor.
In order to correct the above message you need to login to the instance which you were about to specify when pressing Add and go thru the distribution setup wizard first.
For details on how to setup a distribution database click here.
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