Back in the Minecraft Resource Packs menu, move the pack from the "Available" column to the "Selected" column.
Move the ULT_Texture_Pack_PT_6_(INSTALL).zip file directly into that folder. ULT_Texture_Pack_PT_6_(INSTALL).zip
These packs are extremely hardware-intensive. If your game lags, try lowering your shader settings or allocated more RAM to Minecraft (at least 6-8GB is recommended). Back in the Minecraft Resource Packs menu, move