# them ... them ... their

These words refer to those people who have come through the great tribulation.

# the Lamb at the center of the throne will

"the Lamb, who is standing in the middle of the area around the throne, will be"

# For the Lamb ... will shepherd them

"For the Lamb ... will be like a shepherd to them" or "For the Lamb ... will care for them as a person cares for his animals" 

# he will guide them to springs of living water

"he will guide them like a shepherd guiding his sheep to fresh water" or "he will guide them to life like a shepherd guiding his sheep to living water" 

# God will wipe away every tear from their eyes

"God will wipe away their sadness, like wiping away tears" or "God will cause them to not be sad anymore"