Note that calibrators are always found by searching the ALMA calibrator catalogue at project execution time!
There are two options here: either select the System selects calibration strategy option and let the OT decide on which calibrators should be observed and the search criteria used to find them by, or explicitly set the calibrators yourself.
If you wish to set the calibrators yourself, select the User-defined calibration option and use the Add Calibration... button to add calibrators to your goal. Eight different kinds of calibrator target can be added: amplitude, atmospheric, bandpass, delay, focus, phase, pointing and polarization. The search criteria used to identify each type of calibrator can be edited by clicking the appropriate Edit Calibrator Selection Criteria... button in the table, next to the calibrator type. This start the Calibration Query Editor in which the calibrators can be selected. Calibrators can be removed from the list by clicking the Delete Selected Calibration button.