Generating Netlist for Export to Layout
Once your schematics is complete, you want to export the netlist, so that it can be used by the layout tool. To enable the export to the layout tool, go to tools-> Options-> Output and select the Create Netlist checkbox.
Before you are able to export the netlist to annotate it to an Allegro Layout file, you should have an Allegro layout file. You shoudl generate a default blank Allegro layout .brd file. Let the name of this file be x.brd ( You can take allegro PCB tutorial , if you are not familar with Allegro Layout ).
Once you have done that go to File -> Export -> Export Physical in Cadence Design Entry. In the package design check on Repackage. In update PCB Editor board browse to the directory where you just created x.brd and enter x.brd as the Input Board file. In output Board file, select a different name, say, x1.brd. Uncheck BackAnnotate Packaging Properties to Schematics Canvas and click ok.
This will create an updated brd file called x1.brd ( it may be in a different directory - so search for x1.brd in your computer) that you can check and edit in Allegro Layout.
This youtube captures all of the things discussed above.