Installation:

1. Go to Edit > Preferences > Add-ons > Install
2. Press Install Button
3. Find and Select downloaded .zip file
4. Enable the addon

Update to new version:

1. Go to download page of your products and download new version
2. Go to Edit > Preferences > Add-ons > Install
3. Find and Select downloaded .zip file
4. Check this addon is enabled
5. Restart Blender

Usage:

1. Select object in View 3D.
2. Open Sidebar (Press N).
3. Select Item Panel and find Proportional Dimensions.
4. Set X/Y/Z axis to wanted size:

You get proportionally scaled object to new size.

Also you can set any axis to 1:

Open settings to change precise of dimensions: