You can use the LPCOMP.PSEL register to select one of the analog input pins, AIN0 through AIN7, as the analog input pin for the LPCOMP.
See GPIO — General purpose input/output for more information about the pins. Similarly, you can use EXTREFSEL to select one of the analog reference input pins, AIN0 and AIN1, as input for AREF in case AREF is selected in EXTREFSEL. The selected analog pins will be acquired by the LPCOMP when it is enabled through ENABLE.