“carry out the service of Yahweh.” The Hebrew is more literally, “serve the service” (or even, “work the work”) and it refers to worship. The worship of Yahweh was not with hollow words, but with work. The worship of God, as dictated by the Torah, involved the making of sacrifices and offerings, which was a lot of work.

“in his presence.” The Hebrew is literally, “before him,” but it means “in his presence,” and God is in the Tent of Meeting which at this time in history was at Shiloh. The people of the Transjordan tribes knew they would have to go to the Tent of Meeting to serve him. The NIV adds specificity to the text and says, “at His sanctuary.”