What Amaranita Gives You
Amaranita is BetterEnd's wood-like material. The wiki lists Amaranita Cap, Amaranita Fur, Amaranita Hymenophore, Amaranita Hyphae, Amaranita Lantern, and Amaranita Stem. Stems and Hyphae are the log equivalents; Caps are the decorative top pieces; Fur and Hymenophore are secondary drops used in crafting and decoration.
Harvesting
Find an Amaranita forest biome in the End. Chop Amaranita Stems with an axe to get stem blocks, and break Caps for cap blocks. Hyphae appear on the sides of stems. Fur is a softer material you collect from certain Amaranita growths — bring shears if you want to gather it cleanly. Amaranita Lanterns generate naturally in these forests and can be picked up and reused.
Turning It Into a Base
1. Convert Stems into planks the same way you would vanilla logs.
2. Use Hyphae and Caps for textured walls and roofs.
3. Craft Amaranita Lanterns for light that fits the biome's palette.
4. Save Fur and Hymenophore for recipes that call for them rather than burning them as fuel.
5. Replant stems if your version supports it, or rotate between several Amaranita patches to avoid clearing one area.
Amaranita is the most convenient building wood in the End, so establish a grove near your base early.