The keytab file must be accessible from the i5/OS account that is used for EASYCOMD, typically QTCP.
You need to know the location of the keytab file. iseries navigator, and go to "security", and then "Network authentication service". Right-click and select "Manage keytab". Follow the wizard until the last step (you can cancel it if you already done the wizard). The keytab file path is specified in that window.
The typical location is:
/QIBM/UserData/OS400/NetworkAuthentication/keytab/krb5.keytab
To grant access to QTCP you need to do the following command:
CHGAUT OBJ('/QIBM/UserData/OS400/NetworkAuthentication/keytab/krb5.keytab') USER(QTCP) DTAAUT(*R)