BJD_TDB can be calculated by Data Processor and automatically loaded into the Multi-Aperture measurements table by ensuring the following settings are correct. Alternatively, BJD_TDB can be calculated in Multi-Aperture by following this topic:
http://astroimagej.1065399.n5.nabble.com/Add-new-astronomical-values-such-as-BJD-TDB-AIRMASS-etc-to-an-exisiting-measurements-table-td91.html
Enable general FITS header updates and click on the "wrench" icon to the right:
In the panel that opens, make sure BJD_TDB is enabled and that the FITS header keyword name is "BJD_TDB":
In the DP Coordinate Converter panel, enter the target RA/Dec (or SIMBAD resolvable name) and Observatory ID or lat/long:
Now in aperture settings, make sure that "List the following FITS keywords..." is enabled, and that BJD_TDB is in the comma separated list:
Now run DP and Multi-Aperture.