en_tn_condensed/psa/078/071.md

to be shepherd of Jacob, his people, and of Israel, his heritage

The word "shepherd" is a metaphor for one who leads and protects other people. Alternate translation: "to lead and protect the descendants of Jacob, his people, and of Israel, his heritage" (See: rc://en/ta/man/translate/figs-metaphor)

his heritage

"the ones he had chosen to be his forever" See how this is translated in Psalms 78:62.