Since Potomac bundles are defined in Flex Library projects, the normal remoting configuration in application projects isn’t available. Therefore to call a BlazeDS service, you’ll need to specify the necessary parameters at runtime. For BlazeDS remoting, entering the endpoint parameter should be enough. For example:

<mx:RemoteObject desitination="dest" 
endpoint="http://localhost:8080/myBlazeDSApp/messagebroker/amf" />

Read more about this technique here.

One more note, you must also specify the rpc.swc to load as an RSL in your main Potomac application project. Since Potomac bundles do not cause the RPC classes to be statically linked to your main app, you must specify the rpc.swc to load as an RSL. In future drops of Potomac, this will be configured for you automatically.