The usage is very simple please watch this tutorial https://youtu.be/fYuQaj2aUMA

Installation

• Press edit > Preferences > Add ons > Install > select downloaded zip file and enable checkbox
• add-on will be available in the N panel (shortcut - N) by name "World Align"

How to use

1. Select an object
2. Switch to edit mode
3. Select face(s) on one side of object and click "Store Selected Faces" button on "Select Faces From Side 1" panel
4. On "Select Faces From Side 1" panel choose an axis for which Side 1 should be perpendicular
5. Select face(s) on other side of object and click "Store Selected Faces" button on "Select Faces From Side 2" panel
6. On "Select Faces From Side 2" panel choose an axis for which Side 2 should be perpendicular
7. Click "Align" button

Avalibale options

• Rotate
• Bake Rotation
• Center Origin