Your new data extension has to be connected to the contact model of Salesforce when you want to filter the data with it.
To be able to do this you have to connect the data extension via data designer inside contact builder. Therefore you need to create (or edit an existing) attribute group and attach the data extension to it. When you link the data extension to the contact model you click on the top right (inside in an attribute group and configure the relationship). This is shown below:
Link data extension:
- Go into contact Builder
- Go into data designer
- (you may want to create a new attribute group [top right])
- Go into the attribute group
- Click on Data extensions [top right] and click link data extension
- Configure the relationship
After configuring it shows like this:
And if you configured that, you will be able to filter inside journey builder entry source.
Note: This has to be done if you want to filter in the entry event.
When you want to use the dataextension as it is, you can also use
decision splits inside a journey. Here you have the option to use the
shared data extension as filter basis when you select "Journey Data".