Aerie is a custom pipeline for the Canvas renderer. It is not a standalone shader pack, so you turn it on through Canvas rather than through a separate shader menu.
Get the pack loaded
1. Make sure Canvas itself is installed and working. Aerie processes graphics and light through Canvas and needs it to run.
2. Place the Aerie file in your resourcepacks folder. You can open this folder from Options → Resource Packs → Open Pack Folder.
3. Go back to the Resource Packs screen and move Aerie from the left (available) column to the right (selected) column.
4. Click Done and let the game reload its resources.
Select Aerie as the active pipeline
1. Open Canvas's own settings screen. Depending on your setup, you reach it from the video settings or from your mod list.
2. Find the setting that chooses the rendering pipeline. Change it from the default to Aerie.
3. Save and close. Canvas may take a moment to rebuild the world's visuals.
Check that it worked
Load into a world and look at something bright in a dark spot, such as a torch in a cave at night. With Aerie active, bright objects get a soft bloom glow around them. Block shapes and textures keep their normal vanilla look. If nothing looks different, go back and check that the pack is enabled *and* that Aerie is the selected pipeline. Both steps are needed.