# Naomi ... is selling the parcel of land
It was the responsibility of the kinsman to buy back his relative's land and to care for his family. In this case, it meant the man must buy Naomi's land, marry Ruth, and care for Naomi.
# in the presence of
This would make the transaction legal and binding.
# redeem it
This meant to buy the land to keep it within their family.
# I am after you
Boaz was the next kinsman in line to redeem the land.