How can I acquire chlorophyte armour?

You can acquire chlorophyte armour through crafting it at a crafting station. The recipes for the different pieces of armour as follows -

Chlorophyte Bars are crafted from 6 Chlorophyte Ore, an end-game Hardmode ore which can be found in the Underground Jungle, or grown in mud.

The chlorophyte bar crafting recipe -

Sourced from Terraria Wiki on Gamepedia.