Complex sentence: Individuals may accept and receive these ordinances and covenants either during their mortal lives or in the post-mortal spirit world, where they can accept ordinances performed on their behalf by Latter-day Saints in temples.
Split into simpler sentences: Individuals may accept and receive these ordinances and covenants during their mortal lives. For those who did not have the opportunity while living, they will have the opportunity in the post-mortal spirit world, where they can accept ordinances performed on their behalf by Latter-day Saints in temples.