You can easily export your chemical shifts and other project data to a NEF file by going to File / Export / Nef File or using the keyboard shortcut EX. There is no need to include CCPN tags, as this information is not required by the BMRB. You will probably also want to make sure that you are not including Chemical Shift Orphans - these are chemical shifts which are not linked to any peaks and can often be incorrect or temporary assignments that have accumulated during the assignment process. Then deselect all data elements and include only your Chain and Chemical Shifts (which are mandatory). If you like, you can also include peak lists or restraint lists. Choose your file name and path at the bottom of the pop-up and click Save.
For more information on NEF files, see our NEF page.